Conductive elastomer composition, conductive member using conductive elastomer composition, image-forming apparatus having conductive member

ABSTRACT

A conductive elastomer composition includes an ionic-conductive elastomer component, which contains an anion-containing salt having a fluoro group (F—) and a sulfonyl group (—SO 2 —). The conductive elastomer composition has a volume charge not more than 10 8.5  (Ω·cm) when the volume charge is measured at a voltage of 100V applied theretoin accordance with the method specified in JIS K6911. The conductive elastomer composition has a compression set not more than 30% when the compression set is measured at a temperature of 70° C. for 24 hours at a compressibility ratio of 25% in accordance with “the permanent set testing methods for rubber, vulcanized or thermoplastic” specified in JIS K6262.

This application is a divisional of application Ser. No. 10/704,906,filed on Nov. 12, 2003 now U.S. Pat. No. 7,098,264, which claimspriority to application No. 2002-329922 filed in Japan on Nov. 13, 2002.The entire contents of both applications are hereby incorporated byreference and priority is claimed under 35 U.S.C. § 120.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a conductive elastomer composition, aconductive member such as a conductive roller and a conductive beltformed of the conductive elastomer composition, and an image-formingapparatus having the conductive member mounted therein.

More particularly, the present invention relates to the conductiveelastomer composition, which is used effectively for conductive rollerssuch as a development roller, a charging roller, a transfer roller, anda toner supply roller; and for conductive belts such as a transfer belt.The conductive rollers and the conductive belts are used in theimage-forming apparatus such as a copying machine, a printer, afacsimile, and the like. In particular, the present invention providesthe conductive elastomer composition, which is ionic-conductive and hasa much lower electric resistance than the conventional one.

2. Description of the Related Art

It is necessary to allow conductive members such as the charging roller,the development roller, the toner supply roller, the transfer roller,and the transfer belt used in the image-forming apparatus such as thecopying machine, the printer, the facsimile, and the like to have anappropriate stable electric resistance value. As a method of allowingthe conductive roller and the conductive belt to be conductive, thefollowing two methods have been used: In one of the methods, anelectroconductive elastomer composition containing a conductive fillersuch as powder of metal oxides or carbon black is used; and in the othermethod, an ionic-conductive elastomer composition such as urethanerubber, acrylonitrile-butadiene rubber (NBR), and epichlorohydrin rubberis used.

In the case where the electroconductive elastomer composition containingthe conductive filler is used, the electric resistance thereof changesrapidly in a semi-conductive region owing to a slight change of anaddition amount of the conductive filler. Thus it is very difficult tocontrol the electric resistance thereof. In addition, because it isdifficult to disperse the conductive filler uniformly in the elastomercomposition, the electric resistance value has variations in thecircumferential and longitudinal directions of the conductive roller andinside the conductive belt. Further the electric resistance value of theconductive roller and the conductive belt composed of theelectroconductive elastomer composition depends on a voltage appliedthereto and is not constant. The electroconductive elastomer compositioncontaining carbon black shows this phenomenon outstandingly.

Thus as the recent tendency, the ionic-conductive elastomer compositionis used rather than the electroconductive elastomer composition in thecopying machine, the printer and the like required to form a high-imagequality by using digital image processing technique and color imageprocessing technique.

However, it is difficult for the conventional art to reduce the electricresistance value by using only the ionic-conductive elastomer. Thusaddition of an ionic-conductive filler to the ionic-conductive elastomercomponent is proposed. For example, addition of metal ions and aquaternary ammonium salt to the ionic-conductive elastomer component areproposed because only the ionic-conductive elastomer composition such asurethane or NBR makes the electric resistance value too high. Inaddition, other proposals have been made.

For example, in Japanese Patent Application Laid-Open Nos. 2001-214050and 2001-217009, there are disclosed a crosslinked polymeric solidelectrolytic wall made of a conductive polymeric composition consistingof a copolymer containing ethylene oxide at a polymerization ratio notless than 85% and a salt of lithium ions such as a lithium imide saltadded to the copolymer.

In Japanese Patent Application Laid-Open No. 2002-226714, there isdisclosed a polymeric electricity control rubber composition containingvarious elastomers and a specified amount of metal salts added theretowith the intermediary of a specific compound.

However, the conductive polymeric composition disclosed in each ofJapanese Patent Application Laid-Open Nos. 2001-214050 and 2001-217009is used for the wall of a battery. Since the polymerization ratio ofethylene oxide is not less than 85%, the conductive polymericcomposition has a low water resistance and thus can be used in only aclosed system such as the battery. That is, the conductive polymericcomposition cannot be used for products such as the conductive roller,the conductive belt, and the like that are used in an open system havingnormal temperature and humidity. Since the polymerization ratio of theethylene oxide is so high that the conductive polymeric composition hasa high hardness or deterioration in its compression set. Thus it isdifficult to use the conductive polymeric composition for generalproducts or the conductive roller and conductive belt.

The polymeric electricity control rubber composition disclosed inJapanese Patent Application Laid-Open No. 2002-226714 contains thespecific low-molecular weight compound serving as a medium. Thus it doesnot have any problems so long as it is used for general-purpose rubberproducts. However, there is room for improvement in its compression set,stain of a photosensitive member, and the material cost in applying theelectric resistance control rubber composition to products such as theconductive roller, the conductive belt, and the like for use in thecopying machine, the printer, and the like.

There is a possibility that some kind of additives such as metal ions,quaternary ammonium salts, and the like deteriorate the compression setof the ionic-conductive elastomer composition or stain thephotosensitive member and are incapable of reducing the electricresistance value of the ionic-conductive elastomer compositionsufficiently. The additives such as the urethane, NBR, and the like havea high electric resistance value. Thus, the use of these additives donot contribute to realization of such a low volume specific resistancevalue as that specified by the present invention. Therefore theseadditives are unsuitable for conductive members for use in the copyingapparatus, the printer, and the like.

It is conceivable that the ionic-conductive elastomer composition havinga lower electric resistance value than the urethane containsionic-conductive additives such as metal ions and quaternary ammoniumsalts. But this method does not necessarily provide a sufficiently lowelectric resistance value because in dependence on the amount and kindof the ionic-conductive additive, there is much possibility that theproperty of the ionic-conductive elastomer composition such as itscompression set may be deteriorated and the ionic-conductive additivecauses stain of the photosensitive member. In dependence on the mixingamount and kind of the salt, electric resistance value of theionic-conductive elastomer composition increases much in successiveenergization and cannot be put into practical use.

In addition, the conductive members installed on printers of varioustypes are demanded to have various properties besides having a lowelectric resistance value: They are demanded to have favorablemechanical properties such as sufficient wear resistance and strength.Further when they are used in an electrophotographic system, theconductive members for charging toner and a photosensitive drum aredemanded to have appropriate electrostatic property on the surfacesthereof. It is difficult to compose the rubber layer of the conductivemember of only one ionic-conductive elastomer. Thus it is necessary tooptimize the properties of the rubber layer by adding various elastomersto comply with performance demanded in dependence on use.

However, in the case where the above elastomers is added to theionic-conductive elastomer obtained by the conventional art to impartthe above-described demanded properties to the ionic-conductiveelastomer composition, the conductive member composed of the mixture hasa high electric resistance value. Therefore the elastomers are mixedwith the ionic-conductive elastomer in a range in which the mixturesatisfies a predetermined electric resistance value. Consequently themixture is low in its strength and wear resistance.

The development roller and the charging roller are the central componentpart of a printer which forms images by utilizing a static electricity.Thus it is necessary to charge toner and the photosensitive membersufficiently. In addition, the development roller and the chargingroller are demanded to have a low electric resistance value in terms ofthe construction of the printer. Therefore a sufficient amount ofelastomers cannot be added to the ionic-conductive elastomer, asdescribed above. Thus it is impossible to adjust the electrostaticproperty of the surface of the development roller, the charging roller,and the like appropriately. Consequently the toner and thephotosensitive member cannot be sufficiently charged and hence anappropriate image cannot be obtained. Accordingly image deteriorationoccurs during the early stages in a long-term use of the printer.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-describedproblems. Therefore it is a first object of the present invention toprovide a conductive elastomer composition which does not havevariations in electric resistance value, is capable of realizing a lowerelectric resistance value than conventional conductive elastomercompositions, and has a proper hardness without deteriorating propertiesthereof such as a compression set and the like.

It is a second object of the present invention to provide conductivemembers such as a conductive roller, a conductive belt, and a conductiveblade, composed of the conductive elastomer composition, which can besuitably used as a transfer roller, a charging roller, a transfer belt,a cleaning blade, and the like for use in a color copying machine or acolor printer.

To achieve the object, according to a first aspect of the presentinvention, the present invention provides a conductive elastomercomposition including an ionic-conductive elastomer component to whichan anion-containing salt having a fluoro group (F—) and a sulfonyl group(—SO₂—) is added.

The conductive elastomer composition has a volume change not more than10^(6.9) (Ω·cm) when the volume change is measured at a voltage of 100Vapplied thereto in accordance with the method specified in JIS K6911.The conductive elastomer composition has a compression set not more than30% when the compression set is measured at a temperature of 70° C. for24 hours at a compressibility ratio of 25% in accordance with “thepermanent set testing methods for rubber, vulcanized or thermoplastic”specified in JIS K6262. The conductive elastomer composition has ahardness not more than 75 degrees when the hardness is measured by adurometer of type E specified in JIS K6253.

The present inventors have formed a large number of ionic-conductiveadditives and energetically studied various components to be mixed withone another and mixing ratios by making experiments. As a result, theyhave found that by adding the anion-containing salt having the fluorogroup (F—) and the sulfonyl group (—SO₂—) to the ionic-conductiveelastomer component, the anion-containing salt having the fluoro group(F—) and the sulfonyl group (—SO₂—) shows a very high dissociationdegree and a high solubility in the ionic-conductive elastomercomponent. Therefore the conductive elastomer composition is capable ofobtaining a very high conduction degree. Thereby the volume changethereof can be reduced and the properties thereof such as thecompression set and the hardness can be prevented from deteriorating.

Therefore unlike the conventional ionic-conductive elastomercomposition, it is possible to obtain the conductive elastomercomposition having a very low electric resistance value and a lowcompression set. Thus a roller or a belt composed of the conductiveelastomer composition has a proper degree of hardness. That is, theconductive roller and the conductive belt of the present invention havea very low volume change and favorable properties (low compression setand hardness). Thereby power consumption can be reduced and ahigh-quality image having uniform density can be obtained.

Supposing that elastomers are added to the base component of the polymercomponent having a low ionic conduction to allow a conductive member tobe practically used and that the obtained conductive elastomercomposition has a high electric resistance, the anion-containing salthaving the fluoro group (F—) and the sulfonyl group (—SO₂—) is added tothe polymer component to set the volume change of the obtainedconductive elastomer composition to not more than 10^(6.9) (Ω·cm).

The volume change of the conductive elastomer composition is set to notmore than 10^(6.9) (Ω·cm) when the volume change is measured at avoltage of 100V applied thereto in accordance with the method specifiedin JIS K6911. This is for the following reason: If the volume change ofthe conductive elastomer composition is more than 10^(6.9) (Ω·cm), thedevelopment roller, the charging roller, and the like of the copyingapparatus, the printer, and the like are composed of theionic-conductive elastomer, toner and a photosensitive member arecharged at a low efficiency. Thus the development roller, the chargingroller, and the like cannot be put into practical use. For example, letit be supposed that the conductive elastomer composition is used for thedevelopment roller. In this case, when toner charged by the developmentroller having a large electric resistance value is transported to thephotosensitive member from the development roller, a voltage drop islarge. As a result, an electric field having the difference between theelectric potential of the development roller and that of thephotosensitive member becomes small. Thus an image formation cannot bemade as designed. In the case where the ionic-conductive elastomer isused for the charging roller, it is necessary to apply a very largevoltage to the charging roller if its volume change is larger than theabove-described value. Thus the charging roller cannot be put intopractical use.

The lower the volume change, the better. But the lower limit of thevolume change of the conductive elastomer composition is favorably about10^(5.0) (Ω·cm) and more favorably not less than 10^(6.0) (Ω·cm). Thevolume change of the conductive elastomer composition is measured byapplying a voltage of 100V thereto at a constant temperature of 23° C.and a constant relative humidity of 55% in accordance with the methodspecified in JIS K6911.

According to the second aspect of the present invention, there isprovided a conductive elastomer composition having a volume change notmore than 10^(8.5) (Ω·cm), when the volume change is measured at avoltage of 100V applied thereto in accordance with the method specifiedin JIS K6911. The conductive elastomer composition has a compression setnot more than 30% when the compression set is measured at a temperatureof 70° C. for 24 hours at a compressibility ratio of 25% in accordancewith “the permanent set testing methods for rubber, vulcanized orthermoplastic” specified in JIS K6262.

The conductive elastomer composition of the second invention containingtwo or more blended elastomers has a comparatively low volumeresistivity of 10^(8.5) (Ω·cm) and a high charging characteristic. Thusin practical use, the hardness of the conductive elastomer compositionis not limited to the above-described range.

The hardness of the conductive elastomer composition of the secondinvention should be not less than 40 degrees nor more than 88 degreeswhen its hardness is measured by the durometer of type E specified inJIS K6253. To obtain dimensional stability of the nip and a highelectric conduction, the hardness of the conductive elastomercomposition is favorably not less than 45 degrees nor more than 85degrees, more favorably not less than 50 degrees nor more than 80degrees, and most favorably not less than 50 degrees nor more than 70degrees. To obtain the above-described preferable hardness, it is veryadvantageous to use the conductive elastomer composition of the firstinvention.

The conductive elastomer composition formed in this manner has a lowvolume change not more than 10^(8.5) (Ω·cm) when necessary variouselastomers are mixed with the components of the conductive elastomercomposition. Thus as described above, the addition of theanion-containing salt having the fluoro group (F—) and the sulfonylgroup (—SO₂—) to the polymer component is very useful in mixing variouselastomers with the ionic-conductive elastomer to impart a properelectrostatic property to the surface of the development roller and thecharging roller. In the case where various elastomers are mixed with theionic-conductive elastomer obtained by the conventional art, theobtained conductive elastomer composition has a high electricresistance. Thus the conductive roller and the like composed of theelastomer composition cannot be practically used. But the conductiveelastomer composition of the present invention can be formed as theconductive roller that can be practically used. Therefore the presentinvention provides conductive rollers having superior chargingcharacteristic.

In the conductive elastomer composition of present invention, theabove-described salt is added to the ionic-conductive elastomercomponent without the intermediary of polyether compounds such as lowmolecular weight (molecular weight: several hundreds to severalthousands) polyethylene glycol, polypropylene glycol, and polyetherpolyol; and polar compounds such as low molecular weight polyesterpolyol, adipate, and phthalic ester. Therefore the conductive elastomercomposition does not give rise to bleed or transfer contamination. Theconductive roller and the like composed of the conductive elastomercomposition does not stain the photosensitive member of the copyingmachine and the printer.

It is conceivable to dissolve and disperse the above-described salt inpolyether polyol or polyester polyol having a low molecular weight (notmore than 10,000) and make the mixture react with an isocyanate compoundto form polyurethane having a low electric resistance value. But becauseall low molecular weight polyols are incapable of reacting with theisocyanate compound, there is a fear that the photosensitive member isstained. Thus the conductive elastomer composition of the presentinvention is superior in that the above-described salt can be dispersedin the polyether polyol or the polyester polyol without using the lowmolecular weight compound which causes the photosensitive member to bestained and that the conductive elastomer composition has a low electricresistance value. Further, in case of two or more elastomer are blended,the conductive elastomer composition has a volume change not more than10^(8.5) without adding low moleculare weight component.

As described above, the compression set of the conductive elastomercomposition is not more than 30%, more favorably not more than 25%, andmost favorably not more than 20%, when the compression set is measuredat a temperature of 70° C. for 24 hours at a compressibility ratio of25% in accordance with “the permanent set testing methods for rubber,vulcanized or thermoplastic” specified in JIS K6262. It is favorable toset the compression set of the development roller and the chargingroller used or transported in contact with the photosensitive member tonot more than 10%.

If the value of the compression set is more than 30%, the dimensionalchange of the conductive roller and the conductive belt composed of theconductive elastomer composition is so large that they cannot be putinto practical use. In addition, an image-forming system has a problemin its durability and maintenance of accuracy.

The lower limit of the compression set is favorably not less than 1% tooptimize a vulcanizing condition and allow a reliable mass production tobe accomplished.

The conductive elastomer composition has a hardness not more than 75degrees when the hardness is measured by the durometer of type Especified in JIS K6253. This is because the softer the conductiveelastomer composition of the present invention, the larger the nip,which allows transfer, charging, and development to be efficientlyaccomplished. In addition, it is possible to reduce mechanical damage toother members such as the photosensitive member of the printer or thelike. The softer the conductive elastomer composition, the better. Butwhen the conductive elastomer composition is solid, the hardness of theconductive elastomer composition is favorably not less than 40 degreesnor more than 70 degrees and more favorably not less than 50 degrees normore than 70 degrees when the conductive elastomer composition is solid.

The conductive elastomer composition of the present invention has avolume change less than 50%, when the conductive elastomer compositionis immersed in distilled water at 40±1° C. for 22±0.25 hours inaccordance with JIS K6258.

Thereby the conductive elastomer composition is allowed to secure highresistance to water. Thus the conductive elastomer composition iscapable of keeping high performance at a room temperature and a normalhumidity.

It is preferable that the conductive elastomer composition contains notless than 5 nor more than 100 wt % of the ionic-conductive elastomercomponent for 100 wt % thereof. By setting the wt % of theionic-conductive elastomer component to the above range, the conductiveelastomer composition is allowed to have a low volume change. In orderfor the conductive elastomer composition to obtain a low electricresistance, it is most favorable that the conductive elastomercomposition contains about 100 wt % of the ionic-conductive elastomercomponent for 100 wt % thereof. In the case where other polymers areadded to the ionic-conductive elastomer component to stabilizeproduction of the conductive elastomer composition, it is preferablethat the conductive elastomer composition contains not less than 90 normore than 95 wt % of the ionic-conductive elastomer component for 100 wt% thereof. To control the characteristic of the conductive elastomercomposition such as the electrostatic property, the conductive elastomercomposition contains favorably not less than 5 nor more than 80 wt % ofthe ionic-conductive elastomer component for 100 wt % thereof, morefavorably not less than 10 nor more than 50 wt %, and most favorably notless than 10 nor more than 30 wt %.

It is preferable to use a bipolymer of an epihalohydrin-ethylene oxideor a terpolymer of epihalohydrin-ethylene oxide-allyl glycidyl ether asthe ionic-conductive elastomer component.

That is, it is favorable to use epihalohydrin rubber consisting ofepihalohydrin, ethylene oxide, and allyl glycidyl ether copolymerized atthe ratio of 10 to 45 mol %, 55 to 80 mol %, and 0 to 10 mol %respectively.

The above-described copolymerization ratio is set for the reasondescribed below to obtain the above-described volume change withoutdeteriorating the properties (compression set and hardness) of theconductive elastomer composition.

That is, the terpolymer of the epihalohydrin-ethylene oxide-allylglycidyl ether displays the ionic conduction when oxonium ions andpositive metal ions (for example, positive ions such as lithium ionscontained in added salt, nickel ions contained in age resistor forpolymer) in the terpolymer are stabilized by the ethylene oxide unit andtransported by the motion of the segment of the molecular chain at thestabilized portion. Thus the higher the copolymerization ratio of theethylene oxide is, the more ions are stabilized, which allows theconductive elastomer composition to have a low electric resistancevalue.

However, if the copolymerization ratio of the ethylene oxide is toohigh, crystallization of the ethylene oxide occurs, which prevents thesegment motion of the molecular chain from being made. Consequently thevolume specific resistance value increases. The crystallization of theethylene oxide also causes increase of the hardness and deterioration ofthe compression set. To suppress the crystallization of the ethyleneoxide, the copolymerization ratio of the ethylene oxide is set to notmore than 80 mol %. If the copolymerization ratio of the ethylene oxideis less than 55 mol %, the stabilization of the ions is insufficient.Thereby the effect of reducing the volume change is low.

If the copolymerization ratio of the ethylene oxide is more than 80 mol%, the conductive elastomer composition has affinity for water to a veryhigh extent. Thereby the conductive elastomer composition is liable tochange in its configuration and its water resistance owing to moistureabsorption. Thus it is difficult to use the conductive elastomercomposition in environment having the normal temperature and humidity.In this case, the conductive elastomer composition is unsuitable for theuse thereof intended by the present invention. Further if thecopolymerization ratio of the ethylene oxide is more than 80 mol %, theconductive elastomer composition becomes tacky. Consequently theconductive roller and the conductive belt composed of the conductiveelastomer composition may stain the photosensitive member. It is morefavorable that the copolymerization ratio of the ethylene oxide is notless than 65 mol % nor more than 75%.

If the copolymerization ratio of the epihalohydrin is more than 45 mol%, the copolymerization ratio of the ethylene oxide cannot be set to notless than 55 mol %, which makes it difficult to obtain the effect of theethylene oxide. On the other hand, if the copolymerization ratio of theepihalohydrin is less than 10 mol %, the copolymerization ratio of theethylene oxide cannot be set to not more than 80 mol %, which causes theabove-described problem to occur. It is more favorable to set thecopolymerization ratio of the epihalohydrin to not more than 15 mol %nor more than 35 mol %.

It is favorable to use a terpolymer of the epichlorohydrin-ethyleneoxide-allyl glycidyl ether as the ionic-conductive elastomer component.That is, epichlorohydrin is used as the epihalohydrin. Because theepichlorohydrin can be produced easily, the terpolymer of theepichlorohydrin-ethylene oxide-allyl glycidyl ether can be easilyobtained. By copolymerizing the epichlorohydrin, the ethylene oxide, andthe allyl glycidyl ether at the above-described ratio, the conductiveelastomer composition is allowed to have a low electric resistance.

The copolymerization of the allyl glycidyl ether with the epihalohydrinand the ethylene oxide allows crosslinking to be accomplished. Therebythe conductive elastomer composition hardly bleeds or stains thephotosensitive member and is allowed to have rubber-like elasticity.That is, the conductive elastomer composition has improved property. Theallyl glycidyl ether unit itself obtains a free volume as the sidechain. Thus it is possible to control the crystallization of theethylene oxide. Thus the conductive elastomer composition is capable ofrealizing a much lower electric resistance than that obtained by theconventional art.

If the copolymerization ratio of the allyl glycidyl ether exceeds 10 mol%, the number of crosslinking points increases after vulcanization isperformed, which makes it difficult to realize a low electricresistance. Further the conductive elastomer composition is liable tohave deteriorated tensile strength, fatigue characteristic, and flexingresistance. It is favorable to set the copolymerization ratio of theallyl glycidyl ether to not less than 2 mol %. If the copolymerizationratio of the allyl glycidyl ether is less than 2 mol %, bleeding, stainof the photosensitive member, and crystallization of the ethylene oxideare liable to occur. Thus it is difficult to allow the conductiveelastomer composition to have a low electric resistance value. Furtherit is difficult to make the vulcanization speed high, which deterioratesthe productivity the conductive elastomer composition.

By copolymerizing the allyl glycidyl ether with the epihalohydrin andthe ethylene oxide, it is possible to suppress the crystallization ofethylene oxide and reduce the volume specific resistance value. Thecopolymerization of the allyl glycidyl ether with the epihalohydrin andthe ethylene oxide also allows introduction of the double bond of carbonatoms. Thereby crosslinking of the terpolymer with other rubbers can bemade. By co-crosslinking the terpolymer with other rubbers, it ispossible to prevent bleeding from occurring and the photosensitivemember from being stained. It is also possible to increase the molecularweight of the conductive elastomer composition and thus prevent thebleeding and the stain of the photosensitive member to a higher extent.

It is favorable that the conductive elastomer composition contains notless than 0.01 nor more than 20 parts by weight of the anion-containingsalt having the fluoro group (F—) and the sulfonyl group (—SO₂—) for 100parts by weight of an entire polymer component containing theionic-conductive elastomer component.

If the conductive elastomer composition contains less than 0.01 parts byweight of the salt for 100 parts by weight of the entire polymercomponent, the effect of improving the conductance can be hardlyobtained. On the other hand, if the conductive elastomer compositioncontains more than 20 parts by weight of the salt for 100 parts byweight thereof, the material cost increases although the conductance ofthe conductive elastomer composition is improved.

The conductive elastomer composition contains the salt having the fluorogroup (F—) and the sulfonyl group (—SO₂—) at more favorably not lessthan 0.2 nor more than 10 parts by weight and at more favorably not lessthan 0.4 nor more than 6 parts by weight for 100 parts by weight of theentire polymer component.

It is preferable that the anion-containing salt having the fluoro group(F—) and the sulfonyl group (—SO₂—) includes at least one salt selectedfrom among a salt of bisfluoroalkylsulfonylimide, a salt of tris(fluoroalkylsulfonyl) methane, and a salt of fluoroalkylsulfonic acid.

In the above-described salts, anions are stable because the electriccharge are not localized owing to a strong electron attraction effect.Thus the salts show a high degree of dissociation in a polyethyleneoxide and allow the conductive elastomer composition to have a very highionic conductance. It is possible to realize a low electric resistanceefficiently by using the anion-containing salt having the fluoro group(F—) and the sulfonyl group (—SO₂—). Thus by appropriately adjusting themixing ratio of the polymer component, the conductive elastomercomposition is capable of maintaining a low electric resistance andsuppressing the stain of the photosensitive member.

Lithium salts are preferable as the anion-containing salt having thefluoro group (F—) and the sulfonyl group (—SO₂—). Salts of the alkalimetals, the group 2A metals, and other metals may be used as theanion-containing salt having the fluoro group (F—) and the sulfonylgroup (—SO₂—). The conductive elastomer composition may contain saltshaving cations shown by the following formulas 1 and 2. The referencesymbols R₁ through R₆ show alkyl group having 1 to 20 carbon atoms orits derivatives. R₁ through R₄ may be identical to or different fromeach other. Similarly, R₅ and R₆ may be identical to or different fromeach other. It is particularly preferable to use a salt containingtrimethyl-type quaternary ammonium cations consisting of three of R₁through R₆ and one alkyl group or its derivative having favorably 4 to20 carbon atoms and more favorably 6 to 20 carbon atoms. This is becausethree methyl groups, having strong electron-donating property, of thesalt is capable of stabilizing the positive electric charge of nitrogenatoms. In addition, the alkyl group or its derivative is capable ofimproving compatibility of the salt with the ionic-conductive elastomercomponent. In the cations shown by the chemical formula 2, it ispreferable that R₅ or R₆ consists of methyl group or ethyl group becausethe alkyl group or its derivatives R₅ or R₆ having a strongerelectron-donating property is capable of stabilizing the positiveelectric charge of nitrogen atoms. By stabilizing the positive electriccharge of the nitrogen atoms, it is possible to increase the degree ofstability of the cations and thereby form salts having a higherdissociation degree and superior conductance-imparting performance.

As the anion-containing salt having the fluoro group (F—) and thesulfonyl group (—SO₂—), LiCF₃SO₃, LiN(SO₂CF₃)₂, LiC(SO₂CF₃)₃,LiCH(SO₂CF₃)₃, and LiSF₅CF₂SO₃ can be used.

It is preferable that the anion-containing salt having the fluoro group(F—) and the sulfonyl group (—SO₂—) is dispersed uniformly in theelastomer component. Of the above-described salts, the salt ofbisfluoroalkylsulfonylimide such as LiN(SO₂CF₃)₂ is preferable becauseit has a high solubility in the chain of the polyethylene oxide and iscapable of plasticizing the chain of the polyethylene oxide. Thus byadding the salt having the fluoro group (F—) and the sulfonyl group(—SO₂—) to the ionic-conductive elastomer component, it is possible toreduce the hardness of the conductive elastomer composition and reducethe dependence of the volume specific resistance value on environment.In particular, lithium-bis (trifluoromethanesulfonyl) imide(LiN(SO₂CF₃)₂) can be readily dispersed in the elastomer component byadding it directly to ionic-conductive rubber such as epihalohydrinrubber. Thereby it is possible to reduce the compression set of theconductive elastomer composition without adversely affecting thehardness thereof. Thus the lithium-bis (trifluoromethanesulfonyl) imidecan be preferably used.

As the ionic-conductive elastomer component, it is possible to use theterpolymer of the epichlorohydrin-ethylene oxide-allyl glycidyl ethersingly or a mixture of chloroprene rubber and the terpolymer of theepichlorohydrin-ethylene oxide-allyl glycidyl ether. By using theterpolymer of the epichlorohydrin-ethylene oxide-allyl glycidyl ether incombination with chloroprene rubber, it is possible to easily controlthe electric resistance value of the conductive elastomer compositionand the vulcanizing speed. Since the chloroprene rubber is used as ageneral-purpose rubber and inexpensive, the material cost can bereduced. To obtain a low volume change, it is preferable to set theweight ratio between the terpolymer of the epichlorohydrin-ethyleneoxide-allyl glycidyl ether and the chloroprene rubber to 50:50 to 100:0.

One or more of the following rubbers can be mixed with the terpolymer ofthe epichlorohydrin-ethylene oxide-allyl glycidyl ether: acrylonitrilebutadiene rubber, ethylene-propylene-diene terpolymer (EPDM), naturalrubber, isoprene rubber, stylene-butadiene rubber, butyl rubber, andacrylic rubber.

It is preferable to crosslink the terpolymer of theepichlorohydrin-ethylene oxide-allyl glycidyl ether with sulfur andthiourea derivatives or with the sulfur and triazine derivatives orcrosslink the mixture of chloroprene rubber and theepichlorohydrin-ethylene oxide-allyl glycidyl ether with the sulfur andthe thiourea derivatives or with the sulfur and the triazinederivatives. Thereby it is possible to adjust the crosslinking speed,the compression set, and the electric resistance value to a necessarylevel respectively by making use of the advantage of each crosslinkingsystem and selecting the mixing ratio between the sulfur and thethiourea derivatives and the mixing ratio between the sulfur and thetriazine derivatives. In forming a roller composed of a foamed material,it is possible to greatly suppress reduction of the vulcanizing speedand reduction of crosslinking density caused by the use of a foamingagent. Thereby it is possible to obtain the roller composed of thefoamed material having a high strength and a very favorable shape.

As the thiourea derivatives, one or a plurality of thiourea derivativescan be selected from among the group of tetramethylthiourea,trimethylthiourea, ethylenethiourea, and thiourea derivatives indicatedby (C_(n)H_(2n+1)NH)₂C=S (n=integers 1 to 10).

As the triazine derivatives, one or a plurality of compounds can beselected from among the group of 2,4,6-trimelcapto-S-triazine,2-dialkylamino-4,6-dimelcapto-S-triazine. In terms of the vulcanizingspeed, the 2-dialkylamino-4,6-dimelcapto-S-triazine is preferable.

A proper mixing ratio between the sulfur and the thiourea and betweenthe sulfur and the triazine derivatives can be selected in dependence onthe kind of an accelerator.

More specifically, the sulfur is mixed with the entire polymer componentcontaining the ionic-conductive elastomer component at favorably notless than 0.1 nor more than 5.0 parts by weight and at more favorablynot less than 0.2 nor more than 2 parts by weight for 100 parts byweight of the entire polymer component.

If less than 0.1 parts by weight of the sulfur is mixed with 100 partsby weight of the entire polymer component, the entire polymer componentis crosslinked at a low speed, and hence the productivity is low. On theother hand, if more than 5.0 parts by weight of the sulfur is mixed with100 parts by weight of the entire polymer component, there is apossibility that the conductive elastomer composition has a highcompression set and that the sulfur and the accelerator bloom.

The thiourea derivatives are mixed with the polymer component atfavorably not less than 0.0009 mol nor more than 0.0800 mol and at morefavorably not less than 0.0015 mol nor more than 0.0400 mol for 100 g ofthe entire polymer component.

The triazine derivatives is mixed with the polymer component atfavorably not less than 0.0004 mol nor more than 0.0500 mol and at morefavorably not less than 0.0010 mol nor more than 0.0300 mol for 100 g ofthe entire polymer component.

By using the thiourea derivatives and the triazine derivatives in theabove range for 100 g of the polymer component, it is possible to makethe vulcanization tight and suppress blooming and stain of thephotosensitive member. Further the molecular motion is not preventedmuch. Thus the conductive elastomer composition is capable of obtaininga low electric resistance and improving its dynamic property such as thecompression set.

When the conductive elastomer composition is formed into a roller or abelt from foams 2, 3, and 6 by adding a foaming agent thereto, it ispossible to reduce crosslinking inhibition which is caused by thefoaming agent and obtain a sufficiently high vulcanizing speed inpractical use. The foams 2, 3, and 6 will be described later withreference to FIG. 6.

It is preferable to mix the sulfur and the thiourea derivatives at aweight ratio of 5:1 to 1:8. It is preferable to mix the sulfur and thetriazine derivatives at a weight ratio of 3:1 to 1:2.

To improve the dependence of the electric resistance value of theconductive elastomer composition of the present invention onenvironment, it may contain a proper amount of an ionic-conductive agentsuch as carbon black and conductive zinc so long as the ionic conductionthereof does not deteriorate completely.

In performing successive vulcanization, it is suitable to use thethiourea derivatives, the sulfur in combination with thioureaderivatives, and the sulfur in combination with the triazine derivativesbecause an appropriately short scorch time is required.

In addition to using the conductive elastomer composition of the presentinvention as the vulcanized rubber, it can be used as a thermoplasticelastomer composition by dynamically crosslinking it. In this case, asthe matrix resin, polyamide thermoplastic elastomer or thermoplasticpolyurethane can be preferably used.

A part of cations generated from the anion-containing salt having thefluoro group (F—) and the sulfonyl group (—SO₂—) is single-ionized tostabilize the conduction of the conductive elastomer composition andimprove its conduction when a small amount of the salt is added to theionic-conductive elastomer component. It is favorable to single-ionizenot less than 0.5% of the cations. Thereby it is possible for theconductive elastomer composition to obtain a stable conduction to ahigher extent and a lower electric resistance value owing to theaddition of a smaller amount of the metal salt to the ionic-conductiveelastomer component. It is more favorable to single-ionize not less than1% nor more than 20% of the cations.

Single ionization means that an ion adsorbent adsorbs cations or anionsgenerated by dissociation of the salt and thereby cations or anions notadsorbed can move comparatively freely in a system.

To make the vulcanizing speed high, it is preferable to use a sulfurvulcanizing system, a vulcanizing system using the sulfur and thethiourea derivatives in combination or a vulcanizing system using thesulfur and the triazine derivatives in combination. It is preferable touse hydrotalcite to suppress the stain of the photosensitive member.Vulcanization can be performed by known methods. For example, thevulcanization can be performed in a vulcanizing can pressurized by watervapor. A secondary vulcanization may be performed as necessary. It ispossible to carry out a successive vulcanization method in dependence ona mixing ratio.

Hydrotalcite is added to a halogen-containing polymer at favorably notless than 1 nor more than 15 parts by weight and at more favorably notless than 2 nor more than 10 parts by weight for 100 parts by weight ofthe halogen-containing polymer. The hydrotalcite serving as aacid-receiving agent captures halogen-caused ions generated when thehalogen-containing polymer such as epihalohydrin rubber is vulcanized,thus preventing vulcanization from being inhibited and thephotosensitive member from being stained. The hydrotalcite is favorablein its dispersibility. Thus owing to the addition of the hydrotalcite tothe halogen-containing polymer, the property of the conductive elastomercomposition is hardly affected by a kneading state or processing.

The present invention provides conductive members such as the conductiveroller and the conductive belt composed of the conductive elastomercomposition.

The conductive elastomer composition of the present invention issuperior in that it has a low volume change, a low compression set, anda low hardness. Thus the conductive roller composed of the conductiveelastomer composition has a low electric resistance value. Consequentlythe conductive roller can be suitably used as rollers, for a colorprinter or the like, required to have a low electric resistance value.The rollers include a transfer roller, a charging roller, a toner supplyroller, and a development roller; and a transfer belt.

The conductive elastomer composition of the present invention can beformed by using two or more kinds of elastomer components containingelectrostatic property-imparting elastomers. Thus the conductiveelastomer composition can be suitably used as the charging roller forcharging the photosensitive member and the development roller forcharging toner and transporting an electrostatic latent image formed onthe photosensitive member.

Therefore it is possible to design the conductive roller and theconductive belt having desired performance at a very high degree offreedom.

The conductive roller can be produced by conventional methods. Forexample, the conductive elastomer composition (kneaded components) ispreformed tubularly with a single-axis extruder. Then the preform isvulcanized at 160° C. for 15–70 minutes. Thereafter a core metal isinserted into a hollow portion of the vulcanized tube. After the surfaceof the tube is polished, the tube is cut to a predetermined size toobtain a roller. An optimum vulcanizing time period should be set byusing a vulcanization testing rheometer (for example, Curelastometer).The vulcanization temperature may be set around 160° C. in dependence onnecessity. To suppress the stain of the photosensitive member and reducethe compression set of the conductive elastomer composition, it ispreferable to set conditions of the vulcanization temperature and thevulcanization time period so that sufficient vulcanization can beaccomplished. In order for the conductive roller composed of theconductive elastomer to have a low electric resistance value specifiedin the present invention, the electric resistance value thereof isfavorably not less than 10^(3.5) Ω nor more than 10^(5.5) Ω and morefavorably not less than 10^(4.0) Ω nor more than 10^(5.0) Ω when avoltage of 100V is applied thereto.

The conductive belt can be produced by conventional methods. That is,the conductive elastomer composition (kneaded components) is extrudedinto the shape of a belt by an extruder. Then the preform is vulcanizedat 160° C. for 15–70 minutes. The vulcanization temperature may be setaround 160° C. in dependence on necessity.

The electric resistance value of the conductive roller such as thedevelopment roller and the charging roller is favorably not less than10^(5.0) Ω nor more than 10^(7.0) Ω and more favorably not less than10^(5.0) Ω nor more than 10^(6.5) Ω, when a voltage of 100V is appliedthereto so that the conductive roller has favorable electrostaticproperty. If the electric resistance thereof is smaller than 10^(5.0) Ω,too much electric current flows therethrough and hence a defective imageis liable to be formed. Further there is a possibility of discharge tothe photosensitive member. On the other hand, if the electric resistancevalue thereof is larger than 10^(7.0) Ω, toner is inefficiently suppliedto the photosensitive member and thus the conductive roller isunsuitable for practical use. Further when the toner is transferred tothe photosensitive member, the development roller has a voltage drop,which prevents reliable transport of the toner from the developmentroller to the photosensitive member. Consequently a defective image isformed.

As described above, the dielectric loss tangent of the conductive rollerof the present invention is set to 0.1 to 1.5. The dielectric losstangent which is one of the electrical characteristics of the rubberroller means an index indicating the flowability of electricity(dielectric constant) and the degree of influence of a capacitorcomponent (electrostatic capacity). In other words, the dielectric losstangent is a parameter indicating a phase delay when an alternatingcurrent is applied to the development roller, namely, the rate of thecapacitor component (electrostatic capacity) when a voltage is appliedto the rubber roller. That is, the dielectric loss tangent of the rubberroller is indicated by a charged quantity of toner generated when thetoner contacts the development roller through an amount regulation bladeat a high voltage and by a charged quantity thereof which escapes to hedevelopment roller before the toner is transported to the photosensitivemember. Therefore, the dielectric loss tangent is an index indicatingthe charged quantity of the toner immediately before the toner contactsthe photosensitive member. When the dielectric loss tangent is large, itis easy to flow electricity (electric charge) through the rubber roller,which makes the progress of polarization slow. On the other hand, whenthe dielectric loss tangent is small, it is not easy to flow electricitytherethrough, which makes the progress of polarization high.

Therefore the rubber roller having a small dielectric loss tangent iscapable of having a capacitor-like property and maintaining the chargeof the toner generated by a frictional charge without allowing escape ofthe charge of the toner from the rubber roller. That is, the rubberroller is capable of imparting electrostatic property to the toner andmaintaining the imparted electrostatic property. To obtain the effect,the dielectric loss tangent is set to favorably less than 1.5 and morefavorably not less than 0.1 nor more than 1.0.

To prevent the conductive elastomer composition from becoming hard owingto increase of a filler or prevent its surface from being deterioratedby formation of an excessively thick oxide film, the dielectric losstangent of the conductive rubber roller is set to not less than 0.1.

It is favorable the conductive member such as the conductive roller andthe conductive belt composed of the conductive elastomer composition hasa surface roughness Rz not less than 1 μm nor more than 8 μm; and asurface friction coefficient in the range from 0.1 to 1.5.

The reason the surface roughness Rz of the conductive member is set tonot less than 1 μm nor more than 8 μm is as follows: If the surfaceroughness Rz of the conductive member is set to less than 8 μm, smallirregularities having a diameter less than the diameter of the toner arepresent on the surface of the conductive roller and the conductive belt.Thereby the toner can be transported uniformly and has a favorableflowability. Consequently it is possible to impart electrostaticproperty at a very high efficiency. On the other hand, if the surfaceroughness Rz thereof is set to more than 8 μm, toner having a diameterabout 10 μm is difficult to separate from the conductive roller and theconductive belt. Further if the toner having the diameter about 10 μm isreused, the toner may adhere to the conductive roller and the conductivebelt. If the surface roughness Rz thereof is set to less than 1 μm, theconductive roller and the conductive belt are incapable of transportingthe toner sufficiently. As a result, printing dot is unstable. It ismore favorable that the surface roughness Rz of the conductive member isset to not less than 2 μm nor more than 5 μm.

The surface roughness Rz of the conductive member is measured inconformity to JIS B0601 (1994).

The reason the surface friction coefficient of the conductive member isset to 0.1 to 1.5 is as follows: If the surface friction coefficientthereof exceeds 1.5, it is impossible to reduce a stress such as a shearforce to which toner is subjected between the development roller and thetoner supply roller as well as the amount regulation blade. Furtherseparation of the toner from the development roller is unfavorable,which causes deterioration of the toner in long-time (durable) use. Onthe other hand, if the surface friction coefficient thereof is less than0.1, the toner slips and thus a sufficient amount of the toner cannot betransported, which causes printing density low.

It is preferable that the surface of the conductive member consists ofan oxide film. It is preferable that the oxide film has C═O groups andC—O groups. The oxide film serves as a means for charging the tonersufficiently. Further the oxide film functions as a dielectric layer,thus preventing escape of the electric charge. Thus the oxide film iseffective for reducing the friction coefficient and adjusting thedielectric loss tangent of the conductive member.

It is favorable that the oxide film is formed on the surface of theconductive by irradiating the surface with ultraviolet rays and/orozone. The ultraviolet rays are more favorable than the ozone becausethe formation of the oxide film by using the former takes shorter periodof time and costs lower. The processing for forming the oxide film canbe performed by using known methods. For example, the surface of theconductive should be irradiated with the ultraviolet rays having awavelength of favorably 100 nm to 400 nm and more favorably 100 nm to200 nm for 30 seconds to 30 minutes and favorably 1 to 10 minutes,although the wavelength varies according to the distance between thesurface of the conductive and an ultraviolet ray irradiation lamp andaccording to the kind of rubber. The intensity of the ultraviolet raysand the irradiation condition (time period, temperature in bath,distance) are selected according to the dielectric loss tangent and thefriction coefficient specified in the present invention.

The present invention provides an image-forming apparatus having theconductive member such as the conductive roller, the conductive belt,and the like formed of the conductive elastomer composition of thepresent invention.

As the conductive roller, it is possible to list a charging roller foruniformly charging a photosensitive drum, a development roller forcharging toner and transporting it to the photosensitive member, atransfer roller for transferring a toner image from the photosensitivemember to paper or an intermediate transfer belt, and a toner supplyroller for transporting the toner. As the conductive belt, it ispossible to list a transfer belt, an intermediate transfer belt, and afixing belt. The toner and the photosensitive member are charged ordischarged by bringing the surface of the conductive member into contacttherewith. The image-forming apparatus such as a copying machine, aprinter, a facsimile, and the like have preferable electricalcharacteristics because the conductive member of the present inventionis installed therein. Thus the image-forming apparatus has small powerconsumption, thus providing uniform images for a long time.

As apparent from the foregoing description, according to the presentinvention, the anion-containing salt having the fluoro group (F—) andthe sulfonyl group (—SO₂—) is added to the ionic-conductive elastomercomponent providing uniform and stable electric resistance. Thereforethe conductive elastomer composition is capable of obtaining a very highconduction degree. Thus although the conductive elastomer composition isionic-conductive, it has a very low volume specific resistance value anda low compression set. Further the conductive elastomer composition hasa hardness suitable for composing the conductive roller and theconductive belt.

The predetermined parts by weight of the anion-containing salt havingthe fluoro group (F—) and the sulfonyl group (—SO₂—) is added to theionic-conductive elastomer component, namely, theepichlorohydrin-ethylene oxide-allyl glycidyl ether copolymerized at therequired ratio. The predetermined parts by weight of theanion-containing salt having the fluoro group (F—) and the sulfonylgroup (—SO₂—) is added to the mixture of the epichlorohydrin-ethyleneoxide-allyl glycidyl ether and the chloroprene having a lowerconductivity than the epichlorohydrin-ethylene oxide-allyl glycidylether or/and the mixture of the epichlorohydrin-ethylene oxide-allylglycidyl ether and the nonionic elastomer. Thus the conductive elastomercomposition of the present invention has a low volume change.

As apparent from the foregoing description, the conductive elastomercomposition of the present invention has a low electric resistance whichcannot be realized by the conventional one. Thus it can be used forvarious uses. More specifically, the charging roller, the developmentroller, the toner supply roller, the conductive belt, and the likecomposed of the conductive elastomer composition have small powerconsumption and contribute to formation of preferable images havinguniform density. The conductive elastomer composition can be usedsuitably for composing the conductive roller and the conductive beltsuch as the charging roller, the development roller, the toner supplyroller, the transfer belt, and the transfer roller for use in a colorcopying apparatus and a color printer. This is because the conductiveelastomer composition has a comparatively low electric resistance.Therefore the present invention provides image-forming apparatuses suchas the copying apparatus, the printer, the facsimile, and the like thathave small power consumption and provide preferable and high-qualityimages having uniform density reliably for a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a conductive roller of the presentinvention.

FIG. 2 is a schematic view showing a conductive belt of the presentinvention.

FIG. 3 shows the structure of non-chlorine quaternary ammonium salt usedin a comparison example.

FIG. 4 shows the structure of quaternary ammonium perchlorate used in acomparison example.

FIG. 5 is a schematic view showing an apparatus for measuring anelectric resistance value of a conductive roller.

FIG. 6 shows vulcanization curves of foams 1 through 6 obtained by aCurelastometer.

FIG. 7 is a schematic view showing a method of measuring the dielectricloss tangent of the conductive roller.

FIG. 8 is a schematic view showing a method of measuring the frictioncoefficient of the conductive roller.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will be described below withreference to the drawings.

To form the ionic-conductive elastomer component, epichlorohydrin(hereinafter referred to as EP), ethylene oxide (hereinafter referred toas EO), and allyl glycidyl ether (hereinafter referred to as AGE)copolymerized at the ratio of 23 mol %, 73 mol %, and 4 mol %respectively is used as the epihalohydrin rubber consisting ofepihalohydrin, ethylene oxide, and allyl glycidyl ether copolymerized atthe ratio of 10 to 45 mol % 55 to 80 mol %, and 0 to 10 mol %respectively.

As the anion-containing salt having the fluoro group (F—) and thesulfonyl group (—SO₂—), two parts by weight of the lithium-bis(trifluoromethanesulfonyl) imide is added to 100 parts by weight of theepichlorohydrin rubber.

The elastomer component serving as the base component consists of theepichlorohydrin rubber. Thus the anion-containing salt having the fluorogroup (F—) and the sulfonyl group (—SO₂—) is dispersed uniformly in thebase component without using the low molecular weight polyether compoundor the low molecular weight polar compound disclosed in Japanese PatentApplication Laid-Open No. 2002-226714.

After a vulcanizing agent, a vulcanizing accelerator, and additives(inorganic filler, hydrotalcite, zinc oxide, stearic acid) are added tothe elastomer component, all the components are fused and kneaded byusing a known rubber kneading apparatus such as an open roll and anenclosed kneader. Thereafter the polymer component is vulcanized toobtain a conductive elastomer composition.

When all the additives and the elastomer component are mixed with oneanother uniformly by the kneading, the anion-containing salt having thefluoro group (F—) and the sulfonyl group (—SO₂—) may be added to themixture. Thereafter the mixture is kneaded to uniformly disperse theanion-containing salt having the fluoro group (F—) and the sulfonylgroup (—SO₂—) in the elastomer component. Alternatively, it is possibleto prepare a master batch containing the polymer component such asepichlorohydrin rubber into which the anion-containing salt having thefluoro group (F—) and the sulfonyl group (—SO₂—) and the additives havebeen kneaded to obtain desired rubber.

It is preferable to use a master batch containing not less than 1 wt %nor more than 40 wt % of the anion-containing salt having the fluorogroup (F—) and the sulfonyl group (—SO₂—) in the case where the additionamount of the anion-containing salt having the fluoro group (F—) and thesulfonyl group (—SO₂—) is as small as less than one part by weight.Thereby it is possible to prevent deviation of a predeterminedconcentration.

The formed conductive elastomer composition has a volume change 10^(6.6)(Ω·cm), when the volume change is measured at a voltage of 100V appliedthereto in accordance with the method specified in JIS K6911. Theconductive elastomer composition has a compression set of 30% when thecompression set is measured at a temperature of 70° C. for 24 hours at acompressibility ratio of 25% in accordance with “the permanent settesting methods for rubber, vulcanized or thermoplastic” specified inJIS K6262. The conductive elastomer composition has a hardness of 75degrees when the hardness is measured by the durometer of type Especified in JIS K6253.

Thereby it is possible to maintain the volume specific resistance valueand compression set of the conductive elastomer composition at a lowvalue respectively and make the rubber roller and the rubber beltcomposed of the conductive elastomer composition have an appropriatehardness.

As shown in FIG. 1, a conductive roller 1 composed of the conductiveelastomer composition is formed. The conductive roller 1 isapproximately cylindrical. A core metal is inserted into a hollowportion of the conductive roller 1.

A kneaded mixture of all the components is taken out from a kneader asan elastomer composition in the form of a ribbon. The elastomercomposition is introduced into an extruder to extrude it as a hollowtube. The tube is cut to a proper length. Thereafter the cut tube isvulcanized at a required temperature for a required time period toobtain a vulcanized rubber tube. A core metal is inserted into thehollow portion of the rubber tube. Thereafter the surface of the rubbertube is polished to obtain the conductive roller 1.

In the embodiment, the conductive roller is constructed as a chargingroller. However, the conductive roller may be constructed as a transferroller, a development roller or a toner supply roller. In addition, afoamed roller can be formed by adding foaming agents to the basecomponent.

As shown in FIG. 2, a conductive belt 3 such as a transfer belt isproduced from the conductive elastomer composition. The conductive belt3 is tight-stretched by two or more pulleys 4. The conductive belt 3serves as a means for delivering a sheet 6 such as paper and a tonerimage by movably holding it on a straight portion 5 thereof disposed atits upper side. The conductive belt 3 transfers toner to paper from aphotosensitive member in dependence on a case.

As image-forming apparatus in which the conductive member of the presentinvention such as the conductive roller and the conductive belt ismounted, it is possible to exemplify a color printer having a transferroller, a charging roller, a photosensitive member, an intermediatetransfer belt, a fixing roller, toner, a mirror, and a cleaning blade;and a monochromatic printer using a transfer roller and a developmentroller. In addition, the conductive member of the present invention canbe used for image-forming apparatuses such as a copying apparatus, aprinter, a facsimile, and the like.

The examples of the present invention and comparison examples will bedescribed below.

The components mixed at the mixing ratio shown in tables 1 and 2 werekneaded to compose a solid conductive roller of the conductive elastomercomposition of each of the examples 1 through 11 of the presentinvention and comparison examples 1 through 6.

A kneaded mixture containing the components was taken out from a kneaderas an elastomer composition in the form of a ribbon. The elastomercomposition was introduced into a roller head extruder to extrude it inthe shape of a sheet. The sheet-shaped elastomer composition wassupplied to a die to perform press vulcanization therefor at 160° C. fora required time period to obtain a slab sheet for evaluating property ofthe conductive elastomer composition of each of the examples 1 through11 and the comparison examples 1 through 6 and a specimen for measuringthe compression set and the hardness thereof.

TABLE 1-1 Components Component (name (=trade name & maker) E1 E2 E3 E4Epichlorohydrin rubber 1 (Trial product) 100 100 100 100 (EP:EO:AGE =23:73:4, Mn = 130000, Mw = 580000) Epichlorohydrin rubber 2 (EP:EO =39:61) Epichlomer D Daiso Inorganic filler 1 Calcium carbonate MaruoCalcium 20 20 20 20 light Kabushiki Kaisha Hydrotalcite-like compoundDHT-4A-2 Kyowa Kagaku Kogyo 3 3 3 3 Kabushiki Kaisha Magnesium oxideMagsarat 150ST Kyowa Kagaku Kogyo Kabushiki Kaisha Zinc oxide Two kindsof zinc Mitsui Kinzoku 5 5 5 5 oxide Kabushiki Kaisha Stearic acid 4931Unichema Australia 1 1 1 1 Lithium-bis (trifluoromethanesulfonyl) imide2 11 2 11 Lithium trifluoromethanesulfonate Lithium-tris(trifluoromethanesulfonyl) methane ion-adsorbing agent Vulcanizing agent1 Powdered sulfur Tsurumi Kagaku Kogyo 1.5 1.5 Kabushiki KaishaVulcanizing accelerator 1 Nocceler DM Ouchi Shinko Kagaku 1.5 1.5 KogyoKabushiki Kaisha Vulcanizing accelerator 2 Nocceler TS Ouchi ShinkoKagaku 0.5 0.5 Kogyo Kabushiki Kaisha Vulcanizing agent 2 Accel 22-SKawaguchi Kagaku Kogyo 2.0 2.0 Kabushiki Kaisha Vulcanizing accelerator3 Nocceler DT Ouchi Shinko Kagaku 1.7 1.7 Kogyo Kabushiki KaishaVulcanizing agent 3 Actor BSH Kawaguchi Kagaku Kogyo Kabushiki KaishaHardness 70 66 71 69 Roller electric resistance value log₁₀R (Ω) 4.8 4.44.5 4.1 Volume specific resistance log₁₀R (Ω · cm) 6.6 6.3 6.4 6.2Compression set (%) 29 27 7 8 Stain of photosensitive member ◯ ◯ ◯ ◯Cost ◯ Δ ◯ Δ Resistance to water (ΔV(distilled water)(%)/determination)30/◯ 33/◯ 28/◯ 32/◯ where E denotes example.

TABLE 1-2 Components Component (name (=trade name & maker) E5 E6 E7 E8Epichlorohydrin rubber 1 (Trial product) 100 100 100 100 (EP:EO:AGE =23:73:4, Mn = 130000, Mw = 580000) Epichlorohydrin rubber 2 (EP:EO =39:61) Epichlomer D Daiso Inorganic filler 1 Calcium carbonate lightMaruo Calcium Kabushiki 20 20 20 20 Kaisha Hydrotalcite-like compoundDHT-4A-2 Kyowa Kagaku Kogyo 3 3 3 3 Kabushiki Kaisha Magnesium oxideMagsarat 150ST Kyowa Kagaku Kogyo Kabushiki Kaisha Zinc oxide Two kindsof zinc oxide Mitsui Kinzoku Kabushiki 5 5 5 5 Kaisha Stearic acid 4931Unichema Australia 1 1 1 1 Lithium-bis (trifluoromethanesulfonyl) imideLithium trifluoromethanesulfonate 11 11 11 Lithium-tris(trifluoromethanesulfonyl) methane 2 ion-adsorbing agent 3 Vulcanizingagent 1 Powdered sulfur Tsurumi Kagaku Kogyo 1.5 1.5 Kabushiki KaishaVulcanizing accelerator 1 Nocceler DM Ouchi Shinko Kagaku 1.5 1.5 KogyoKabushiki Kaisha Vulcanizing accelerator 2 Nocceler TS Ouchi ShinkoKagaku 0.5 0.5 Kogyo Kabushiki Kaisha Vulcanizing agent 2 Accel 22-SKawaguchi Kagaku Kogyo 2.0 2.0 Kabushiki Kaisha Vulcanizing accelerator3 Nocceler DT Ouchi Shinko Kagaku 1.7 1.7 Kogyo Kabushiki KaishaVulcanizing agent 3 Actor BSH Kawaguchi Kagaku Kogyo Kabushiki KaishaHardness 68 70 70 70 Roller electric resistance value log₁₀R (Ω) 4.9 4.64.2 4.1 Volume specific resistance log₁₀R (Ω · cm) 6.7 6.5 6.2 6.2Compression set (%) 27 6 5 27 Stain of photosensitive member ◯ ◯ ◯ ◯Cost ◯ ◯ ◯ Δ Resistance to water (ΔV(distilled water)(%)/determination)34/◯ 33/◯ 31/◯ 31/◯ where E denotes example.

TABLE 1-3 Components Component (name (=trade name & maker) E9 E10 E11Epichlorohydrin rubber 1 (EP:EO:AGE = 23:73:4, (Trial product) 100 100Mn = 130000, Mw = 580000) Epichlorohydrin rubber 2 (EP:EO = 39:61)Epichlomer D Daiso 100 Inorganic filler 1 Calcium carbonate light MaruoCalcium Kabushiki 20 20 20 Kaisha Hydrotalcite-like compound DHT-4A-2Kyowa Kagaku Kogyo 3 3 Kabushiki Kaisha Magnesium oxide Magsarat 150STKyowa Kagaku Kogyo 3 Kabushiki Kaisha Zinc oxide Two kinds of zinc oxideMitsui Kinzoku Kabushiki 5 5 5 Kaisha Stearic acid 4931 UnichemaAustralia 1 1 1 Lithium-bis (trifluoromethanesulfonyl) imide 2 2 2Lithium trifluoromethanesulfonate Lithium-tris(trifluoromethanesulfonyl) methane ion-adsorbing agent Vulcanizing agent1 Powdered sulfur Tsurumi Kagaku Kogyo 0.50 1.00 Kabushiki KaishaVulcanizing accelerator 1 Nocceler DM Ouchi Shinko Kagaku 0.50 1.00Kogyo Kabushiki Kaisha Vulcanizing accelerator 2 Nocceler TS OuchiShinko Kagaku 0.17 0.88 Kogyo Kabushiki Kaisha Vulcanizing agent 2 Accel22-S Kawaguchi Kagaku Kogyo 1.33 2.0 Kabushiki Kaisha Vulcanizingaccelerator 3 Nocceler DT Ouchi Shinko Kagaku 1.13 1.7 Kogyo KabushikiKaisha Vulcanizing agent 3 Actor BSH Kawaguchi Kagaku Kogyo 1.06Kabushiki Kaisha Hardness 71 71 71 Roller electric resistance valuelog₁₀R (Ω) 4.9 4.8 4.9 Volume specific resistance log₁₀R (Ω · cm) 6.76.6 6.7 Compression set (%) 23 22 3 Stain of photosensitive member ◯ ◯ ◯Cost ◯ ◯ ◯ Resistance to water (ΔV(distilled water)(%)/determination)29/◯ 30/◯ 25/◯ where E denotes example.

TABLE 2-1 Components Component (name (=trade name & maker) CE1 CE2 CE3Epichlorohydrin rubber 1 (Trial product) 100 100 (EP:EO:AGE = 23:73:4,Mn = 130000, Mw = 580000) Epichlorohydrin rubber 2 (EP:EO = 39:61)Epichlomer D Daiso Kabushiki Kaisha Epichlorohydrin rubber 3 EpichlomerCG104 Daiso Kabushiki 100 (EP:EO:AGE = 63:34.5:2.5) Kaisha EP-PO-AGEcopolymer (EP:PO:AGE = 90:4:6, ZSN8030 Zeon Mn = 80000, Mw = 400000)Inorganic filler 1 Calcium carbonate Maruo Calcium 20 20 20 lightKabushiki Kaisha Hydrotalcite-like compound DHT-4A-2 Kyowa Kagaku Kogyo3 3 3 Kabushiki Kaisha Zinc oxide Two kinds of zinc Mitsui Kinzoku 5 5 5oxide Kabushiki Kaisha Stearic acid 4931 Unichema Australia 1 1 1Lithium-bis (trifluoromethanesulfonyl) imide 11 Non-chlorine quaternaryammonium salt KP4729 Kao Kabushiki Kaisha 2 Quaternary ammoniumperchlorate A-902 Nippon Carlit Kabushiki Kaisha High-performanceionic-conductive additive Vulcanizing agent 1 Powdered sulfur TsurumiKagaku Kogyo 1.5 1.5 1.5 Vulcanizing accelerator 1 Nocceler DM OuchiShinko Kagaku 1.5 1.5 1.5 Kogyo Kabushiki Kaisha Vulcanizing accelerator2 Nocceler TS Ouchi Shinko Kagaku 0.5 0.5 0.5 Kogyo Kabushiki KaishaVulcanizing agent 2 Accel 22-S Kawaguchi Kagaku Kogyo Kabushiki KaishaVulcanizing accelerator 3 Nocceler DT Ouchi Shinko Kagaku Kogyo Hardness72 72 73 Roller electric resistance value log₁₀R (Ω) 7.2 5.6 5.9 Volumespecific resistance log₁₀R (Ω · cm) 8.3 7.1 7.3 Compression set (%) 3565 41 Stain of photosensitive member ◯ ◯ ◯ Cost ◯ Δ ◯ Resistance towater (ΔV(distilled water)(%)/determination) 23/◯ 42/◯ 32/◯ where CEdenotes comparison example.

TABLE 2-2 Components Component (name (=trade name & maker) CE4 CE5 CE6Epichlorohydrin rubber 1 (Trial product) 100 100 (EP:EO:AGE = 23:73:4,Mn = 130000, Mw = 580000) Epichlorohydrin rubber 2 (EP:EO = 39:61)Epichlomer D Daiso Kabushiki Kaisha Epichlorohydrin rubber 3 EpichlomerCG104 Daiso Kabushiki (EP:EO:AGE = 63:34.5:2.5) Kaisha EP-PO-AGEcopolymer (EP:PO:AGE = 90:4:6, ZSN8030 Zeon 100 Mn = 80000, Mw = 400000)Inorganic filler 1 Calcium carbonate Maruo Calcium 20 20 20 lightKabushiki Kaisha Hydrotalcite-like compound DHT-4A-2 Kyowa Kagaku Kogyo3 3 3 Kabushiki Kaisha Zinc oxide Two kinds of zinc Mitsui Kinzoku 5 5 5oxide Kabushiki Kaisha Stearic acid 4931 Unichema Australia 1 1 1Lithium-bis (trifluoromethanesulfonyl) imide 2 Non-chlorine quaternaryammonium salt KP4729 Kao Kabushiki Kaisha Quaternary ammoniumperchlorate A-902 Nippon Carlit 2 Kabushiki Kaisha High-performanceionic-conductive additive 2 Vulcanizing agent 1 Powdered sulfur TsurumiKagaku Kogyo 1.5 1.5 1.5 Vulcanizing accelerator 1 Nocceler DM OuchiShinko Kagaku 1.5 1.5 1.5 Kogyo Kabushiki Kaisha Vulcanizing accelerator2 Nocceler TS Ouchi Shinko Kagaku 0.5 0.5 0.5 Kogyo Kabushiki KaishaVulcanizing agent 2 Accel 22-S Kawaguchi Kagaku Kogyo Kabushiki KaishaVulcanizing accelerator 3 Nocceler DT Ouchi Shinko Kagaku Kogyo Hardness74 72 83 Roller electric resistance value log₁₀R (Ω) 4.1 4.8 4.9 Volumespecific resistance log₁₀R (Ω · cm) 6.2 6.6 6.7 Compression set (%) 4552 25 Stain of photosensitive member Δ X X Cost ◯ ◯ ◯ Resistance towater (ΔV(distilled water)(%)/determination) 33/◯ 45/◯ 252/X where CEdenotes comparison example.

The numerical values shown in each table indicate parts by weight. Theabbreviation EP denotes epichlorohydrin. EO denotes ethylene oxide. AGEdenotes allyl glycidyl ether. PO denotes propylene oxide. Theabbreviation Mn denotes number-average molecular weight. Mw denotesweight-average molecular weight. In each table, vulcanizing accelerator1 consists of dibenzothiazolyl sulfide. Vulcanizing accelerator 2consists of tetramethylthiuram monosulfide. Vulcanizing accelerator 3consists of di-olto-trilguanidine. Vulcanizing agent 2 consists ofethylene thiourea. Vulcanizing agent 3 consists of2-di-n-butylamino-4,6-dimelcapto-s-triazine.

A trial product obtained by the polymerization described in JapanesePatent Application Laid-Open No. 2000-63656 was used as theepichlorohydrin rubber.

In table 2, the non-chlorine ammonium salt is quaternary ammonium saltof gluconic acid having the structure shown in FIG. 3. The quaternaryammonium perchlorate is quaternary ammonium salt shown in FIG. 4. Thehigh-performance ionic-conductive additive consists of lithium-bis(trifluoromethanesulfonyl) imide dissolved in 20 wt % ofdibutoxyethoxyethyl adipate. The lithium-bis (trifluoromethanesulfonyl)imide in table 2 was synthesized by the conventional method described inJapanese Patent Application Laid-Open No. 2001-288193 was used.

More specifically, an elastomer composition taken out from a kneaderthat kneaded the components mixed at the mixing ratio shown in table 1and 2 was supplied to an extruder having an inner diameter of φ 60 mm toextrude it as a hollow tube. The raw rubber tube was cut to a propersize and vulcanized at 160° C. for 15–70 minutes to obtain a vulcanizedrubber tube.

A cylindrical shaft having the same configuration as that of the shaftof the charging roller mounted on a copying apparatus IMAGIO MF2730produced by Ricoh was prepared. After a hot-melt adhesive agent wasapplied to the shaft, the shaft was inserted into the vulcanized rubbertube and bonded thereto. The surface of the rubber tube was polished toobtain the conductive rubber roller of each of the examples and thecomparison examples having the predetermined size. The dimension of eachconductive rubber roller had an outer diameter of 14 mmφ and an innerdiameter (diameter of shaft) of 8 mmφ. The axial length of theconductive rubber roller was 317 mm which was equal to that of thecharging roller mounted on the copying apparatus IMAGIO MF2730 producedby Ricoh.

EXAMPLES 1 THROUGH 11

As shown in table 1, each of the conductive elastomer composition of theexample 1 through 10 contained the EP-EO-AGE terpolymer having the samecopolymerization ratio (EP:EO:AGE=23:73:4) which falls in the rangespecified in the present invention. The conductive elastomer compositionof the example 11 contained the EP-EO bipolymer (EP:EO=39:61).

In the examples 1 through 4 and 9 through 11, the lithium-bis(trifluoromethanesulfonyl) imide was used as the anion-containing salthaving the fluoro group (F—) and the sulfonyl group (—SO₂—). In theexamples 5 through 7, lithium trifluoromethanesulfonate was used. In theexample 8, lithium-tris (fluoroalkylsulfonyl) methane was used.

The components of each example were mixed with one another at the mixingratio shown in table 1 to obtain the conductive elastomer composition ofeach example.

COMPARiSON EXAMPLE 1 THROUGH 6

As shown in table 2, the conductive elastomer composition of each of thecomparison examples 1, 3, 4, and 5 contained the EP-EO-AGE terpolymerhaving the same copolymerization ratio as that of the example 1. Theconductive elastomer composition of the comparison example 2 containedthe EP-EO-AGE terpolymer (EP:EO:AGE=63:34.5:2.5). The conductiveelastomer composition of the comparison example 6 contained theEO-PO-AGE terpolymer (EO:PO:AGE=90:4:6).

The conductive elastomer composition of each of the comparison examples2 and 6 contained the lithium-bis (trifluoromethanesulfonyl) imide whichis the anion-containing salt having the fluoro group (F—) and thesulfonyl group (—SO₂—).

The conductive elastomer composition of the comparison example 3contained the non-chlorine quaternary ammonium salt. The conductiveelastomer composition of the comparison example 4 contained thequaternary ammonium perchlorate. The conductive elastomer composition ofthe comparison example 5 contained the high-performance ionic-conductiveadditive.

The conductive elastomer composition of the comparison example 1 did notcontain the ionic-conductive additive.

The components of each comparison example were mixed with one another atthe mixing ratio shown in table 2 to obtain the conductive elastomercomposition of each comparison example.

The following properties were measured on the conductive elastomercomposition of each of the examples and the comparison examples. Tables1 and 2 show the results in the lower portion thereof.

Measurement of Hardness

The hardness of the specimen for measuring the compression set of eachconductive elastomer composition was measured by the durometer of type Especified in JIS K6253 by applying a load of 1000 g thereto.

Measurement of Volume Change

The volume change of each of the above-described slab sheets each havinga size of 130 mm×130 mm×2 mm were measured at a constant temperature of23° C. and a constant relative humidity of 55% by an ultra-highresistance micro-ammeter R-8340 manufactured by Advance Test CorporationInc. The measuring method conformed to the method of measuring thevolume change (volume specific resistance) specified in JIS K6911. Theapplied voltage was 100V.

Tables 1 and 2 show the volume change of each slab sheet by commonlogarithm log₁₀R (Ω·cm).

Measurement of Compression Set

In accordance with “the permanent set testing methods for rubber,vulcanized or thermoplastic” specified in JIS K6262, the compression setof each specimen was measured at 70° C. for 24 hours. The compressionrate was 25% of the thickness of the specimen.

The roller composed of the foam (solid specimen) has a large dimensionalchange if the compression set of the foam is not less than 30%. Thus theroller is unsuitable for practical use, although there is a smalldifference in an expansion rate and an expansion mode.

Test of Stain of Photosensitive Member

The slab sheets of the examples and the comparison examples were storedfor two weeks at 32.5° C. and at a relative humidity of 90%, with theslab sheets pressed against a photosensitive member set in a cartridge(cartridge type C4127X) of a laser beam printer of Laser Jet 4050 typeproduced by Hulet Packard Inc. After each vulcanized rubber slab sheetwas removed from the photosensitive member, half-tone printing wascarried out by the printer accommodating the photosensitive member.Whether or not printed sheets of paper were stained was checked with thenaked eye to make evaluation of the slab sheets by the following threecriteria:

-   ◯: Printed paper was not stained with the naked eye.-   Δ: Low degree of stain (when five sheets of paper were printed,    stain was hardly visible and thus there is no problem in use).-   X: High degree of stain (when not less than five sheets of paper    were printed, stain was visible with the naked eye)-   X: High degree of stain (when 11 or more sheets of paper were    printed, stain could be recognized with the eye)    Examination of Resistance to Water

The volume change of the slab sheet of each of the examples and thecomparison examples having a size of 130 mm×130 mm×2 mm was measured byimmersing it in distilled water having a temperature 40±1° C. for22±0.25 hours in accordance with the method specified in JIS K6258.Based on obtained values, the resistance to water of each slab sheet wasdetermined as follows:

The slab sheet having a volume change less than 50% was rated as ◯ (noproblem in resistance to water) and not less than 50% was rated as X(unfavorable in resistance to water).

The electric resistance value of the roller of each of the examples andcomparison examples was measured.

Measurement of Electric Resistance Value of Roller

As shown in FIG. 5, a conductive roller 11 having a core metal 12inserted therethrough was mounted on an aluminum drum 13 having φ30 mm,with the conductive roller 11 in contact with the aluminum drum 13. Theleading end of a conductor, having an internal electric resistance of r(100Ω), which was connected to the positive side of a power source 14was connected to one end surface of the aluminum drum 13. The leadingend of the conductor connected to the negative side of the power source14 was connected to one end surface of the conductive roller 11.Supposing that a voltage applied to the apparatus is E, the electricresistance R of the conductive roller 11 is: R=r×E/(V−r). Because theterm of (−r) is regarded as being slight, R=r×E/V. A load F of 500 g wasapplied to both ends of the core metal 2. The conductive roller 11 wasrotated at 30 rpm. The applied voltage E was the above-described voltage100V. The detected voltage V was measured at 100 times during fourseconds. The electric resistance R was computed by using the aboveequation. The average of resistance values was set as the electricresistance of the conductive roller 11. Tables 1 and 2 show theresistance value of each conductive roller 11 by common logarithmlog₁₀RΩ.

Cost

The material cost of each example and comparison example per volume wascomputed. The material cost of the example 4 was rated as Δ (fair). Thematerial cost higher than the material cost Δ by not less than 10% wasrated as X (unsuitable). The material cost lower than the cost Δ by notless than 10% was rated as ◯ (good). Table 1 and 2 show the results. Thematerial cost higher or lower than the material cost Δ of the example 4by less than 10% was rated as Δ (fair).

As indicated in table 1, the conductive elastomer composition of theexample 1 contained two parts by weight of the lithium-bis(trifluoromethanesulfonyl) imide for 100 parts by weight of theEP-EO-AGE terpolymer having the copolymerization ratio which falls inthe range specified in the present invention, the vulcanizingaccelerator consisting of sulfur and thiazole, and the vulcanizingaccelerator consisting of thiuram. Therefore the conductive elastomercomposition had a low volume specific resistance value, namely, 10^(6.6)(Ω·cm) and a proper compression set and hardness suitable for practicaluse. The rubber roller did not stain the photosensitive member, and thematerial cost was rated as ◯. Thus it was confirmed that the rubberroller of the example 1 was superior in its properties. The volumechange of the slab sheet of the example 1 was 30% when it was measuredby immersing it in distilled water having a temperature 40±1° C. for22±0.25 hours in accordance with the method specified in JIS K6258. Thusthe slab sheet was rated as ◯. That is, the conductive elastomercomposition of the example had no problem in its resistance to water.

The conductive elastomer composition of the example 2 is different fromthat of the example 1 in that the conductive elastomer composition ofthe example 2 contained 11 parts by weight of the lithium-bis(trifluoromethanesulfonyl) imide for 100 parts by weight of theEP-EO-AGE terpolymer. Therefore the conductive elastomer composition hada low volume specific resistance value, namely, 10^(6.3) (Ω·cm) and aproper compression set and hardness for practical use. The rubber rollerdid not stain the photosensitive member. Thus it was confirmed that therubber roller of the example 2 was superior in its properties, althoughthe material cost was rated as Δ. Similarly to the example 1, the slabsheet was rated as ◯. That is, the conductive elastomer composition ofthe example 2 had no problem in its resistance to water.

The conductive elastomer composition of the example 3 is different fromthat of the example 1 in that in the conductive elastomer composition ofthe example 3 contained thiourea derivatives and guanidine used incombination as the vulcanizing accelerator. The conductive elastomercomposition had a low volume specific resistance value, namely, 10^(6.4)(Ω·cm) and a low compression set and a proper hardness suitable forpractical use. Thus it was confirmed that the conductive elastomercomposition of the example 3 was excellent. Further the rubber rollerdid not stain the photosensitive member. The material cost was rated as◯. Thus it was confirmed that the rubber roller had superior properties.The slab sheet made of the conductive elastomer composition had noproblem in its resistance to water.

The conductive elastomer composition of the example 4 is different fromthat of the example 3 in that the conductive elastomer composition ofthe example 4 contained 11 parts by weight of the lithium-bis(trifluoromethanesulfonyl) imide for 100 parts by weight of theEP-EO-AGE terpolymer. The conductive elastomer composition had a verylow volume specific resistance value, namely, 10^(6.2) (Ω·cm) and a lowcompression set and a proper hardness suitable for practical use. Thusthe conductive elastomer composition of the example 4 was excellent.Further the rubber roller did not stain the photosensitive member,although the material cost was rated as Δ. Thus it was confirmed thatthe rubber roller had superior properties. The sheet made of theconductive elastomer composition had no problem in its resistance towater.

The conductive elastomer composition of the example 5 is different fromthat of the example 2 in that instead of the lithium-bis(trifluoromethanesulfonyl) imide, the conductive elastomer compositionof the example 5 contained 11 parts by weight of lithiumtrifluoroalkylmethanesulfonate for 100 parts by weight of the EP-EO-AGEterpolymer. The conductive elastomer composition had a low volumespecific resistance value, namely, 10^(6.7) (Ω·cm) and a propercompression set and hardness suitable for practical use. The rubberroller did not stain the photosensitive member. The material cost wasrated as ◯. Thus it was confirmed that the rubber roller was superior inits properties. The sheet made of the conductive elastomer compositionhad no problem in its resistance to water.

The conductive elastomer composition of the example 6 is different fromthat of the example 4 in that instead of the lithium-bis(trifluoromethanesulfonyl) imide, the conductive elastomer compositionof the example 6 contained 11 parts by weight of lithiumtrifluoroalkylmethanesulfonate for 100 parts by weight of the EP-EO-AGEterpolymer. The conductive elastomer composition had a low volumespecific resistance value, namely, 10^(6.5) (Ω·cm) and a very lowcompression set and hardness suitable for practical use. The rubberroller did not stain the photosensitive member. The material cost wasrated as ◯. Thus it was confirmed that the rubber roller was superior inits properties because. The sheet made of the conductive elastomercomposition had no problem in its resistance to water.

The conductive elastomer composition of the example 7 is different fromthat of the example 6 in that the conductive elastomer composition ofthe example 7 contained an anion-adsorbing agent. The conductiveelastomer composition had a low volume specific resistance value,namely, 10^(6.2) (Ω·cm) and a very low compression set and hardnesssuitable for practical use. The rubber roller did not stain thephotosensitive member. The material cost was rated as ◯. Thus it wasconfirmed that the rubber roller was superior in its properties. Thesheet made of the conductive elastomer composition had no problem in itsresistance to water.

The conductive elastomer composition of the example 8 is different fromthat of the example 1 in that instead of the lithium-bis(trifluoromethanesulfonyl) imide, the conductive elastomer compositionof the example 8 contained two parts by weight of lithium-tris(trifluoromethanesulfonyl) methane for 100 parts by weight of theEP-EO-AGE terpolymer. The conductive elastomer composition had a verylow volume specific resistance value, namely, 10^(6.2) (Ω·cm) and a lowcompression set and a proper hardness suitable for practical use. Thusit was confirmed that the conductive elastomer composition of theexample 8 was excellent. Further the rubber roller did not stain thephotosensitive member, although the material cost was rated as Δ. Thusit was confirmed that the rubber roller had superior properties. Theslab sheet made of the conductive elastomer composition had no problemin its resistance to water.

The conductive elastomer composition of the example 9 is different fromthat of the examples 1 and 3 in that the conductive elastomercomposition of the example 9 contained sulfur and thiourea derivativesused in combination as the vulcanizing agent and the thiazole andthiuram used in combination as the vulcanizing accelerator. Theconductive elastomer composition had a low volume specific resistancevalue, namely, 10^(6.7) (Ω·cm) and a low compression set and a properhardness suitable for practical use. Thus the conductive elastomercomposition of the example 9 was excellent. Further the rubber rollerdid not stain the photosensitive member. The material cost was rated as◯. Thus it was confirmed that the rubber roller composed of theconductive elastomer composition had superior properties. The slab sheetmade of the conductive elastomer composition had no problem in itsresistance to water.

The conductive elastomer composition of the example 10 is different fromthat of the example 1 in that it contained sulfur and thioureaderivatives used in combination as the vulcanizing agent and thiazoleand thiuram used in combination as the vulcanizing accelerator. Theconductive elastomer composition had a low volume specific resistancevalue, namely, 10^(6.6) (Ω·cm) and a low compression set and a properhardness suitable for practical use. Thus the conductive elastomercomposition of the example 10 was excellent. Further the rubber rollerdid not stain the photosensitive member. The material cost was rated as◯. Thus it was confirmed that the rubber roller composed of theconductive elastomer composition had superior properties. The sheet madeof the conductive elastomer composition had no problem in its resistanceto water.

The conductive elastomer composition of the example 11 is different fromthat of the example 3 in that instead of the EP-EO-AGE terpolymer usedin the examples 1 through 10, the conductive elastomer composition ofthe example 11 contained 100 parts by weight of an EP-EO bipolymer(EP:EO=39:61) which fell within the preferable range of thecopolymerization ratio. The conductive elastomer composition had a lowvolume specific resistance value, namely, 10^(6.7) (Ω·cm) and a lowcompression set and a proper hardness suitable for practical use. Thusthe conductive elastomer composition of the example 11 was excellent.Further the rubber roller did not stain the photosensitive member. Thematerial cost was rated as ◯. Thus it was confirmed that the rubberroller composed of the conductive elastomer composition had superiorproperties. The slab sheet made of the conductive elastomer compositionhad no problem in its resistance to water.

In each of the examples 1 through 11, the conductive elastomercomposition had a volume change not more than 10^(6.9) (Ω·cm) when thevolume change was measured at a voltage of 100V applied thereto inaccordance with the method specified in JIS K6911. The conductiveelastomer composition had a compression set not more than 30% when thecompression set was measured at a temperature of 70° C. for 24 hours ata compressibility ratio of 25% in accordance with “the permanent settesting methods for rubber, vulcanized or thermoplastic” specified inJIS K6262. The conductive elastomer composition had a hardness not morethan 75 degrees when the hardness was measured by the durometer of typeE. Further the rubber roller did not stain the photosensitive member andthe material cost was rated as ◯. Thus it was confirmed that the rubberroller of each of the examples 1 through 11 had superior properties.

As the example 7 shows, the conductive elastomer composition containingthe anion-adsorbing agent added to the lithiumtrifluoroalkylmethanesulfonate has a lower volume change lower than theconductive elastomer composition not containing the anion-adsorbingagent. The effect of reducing the volume change obtained by the additionof the anion-adsorbing agent is similar to that of reducing the volumechange obtained by the use of a large amount of the lithium-bis(trifluoromethanesulfonyl) imide. Therefore the conductive elastomercomposition of the example 7 is costly advantageous.

As shown in table 2, the conductive elastomer composition of thecomparison example 1 is different from that of the examples 1, 2, 5, and8 in that the conductive elastomer composition of the comparison example1 did not contain the anion-containing salt having the fluoro group (F—)and the sulfonyl group (—SO₂—). The conductive elastomer composition hada large volume specific resistance value, namely, more than 10^(6.9)Ω·cm. The conductive elastomer composition had a compression set valuelarger than 30%. Thus the conductive elastomer composition wasinappropriate for practical use.

The conductive elastomer composition of the comparison example 2 isdifferent from that of the example 2 in that the copolymerization ratioof the EP-EO-AGE terpolymer was out of the preferable range specified inthe present invention. Although the conductive elastomer compositioncontained 11 parts by weight of the lithium-bis(trifluoromethanesulfonyl) imide, the conductive elastomer compositionhad a large volume specific resistance value, namely, more than 10^(6.9)Ω·cm. The material cost of the conductive elastomer composition wasrated as Δ. The conductive elastomer composition had a very highcompression set.

The conductive elastomer composition of the comparison example 3 isdifferent from that of the examples 1, 2, 5, and 8 in that theconductive elastomer composition of the comparison example 3 contained anon-chlorine ammonium salt instead of the anion-containing salt havingthe fluoro group (F—) and the sulfonyl group (—SO₂—). The conductiveelastomer composition had a large volume specific resistance value,namely, more than 10^(6.9) Ω·cm. Further the conductive elastomercomposition had a considerably high compression set.

The conductive elastomer composition of the comparison example 4 isdifferent from that of the examples 1, 2, 5, and 8 in that theconductive elastomer composition of the comparison example 4 containedammonium perchlorate instead of the anion-containing salt having thefluoro group (F—) and the sulfonyl group (—SO₂—). The conductiveelastomer composition had a considerably high compression set and wasinappropriate for practical use.

The conductive elastomer composition of the comparison example 5 isdifferent from that of the examples 1, 2, 5, and 8 in that theanion-containing salt having the fluoro group (F—) and the sulfonylgroup (—SO₂—) was not added to the ionic-conductive elastomer component,but was used in the form of a high-performance ionic-conductive additivein which the anion-containing salt having the fluoro group (F—) and thesulfonyl group (—SO₂—) was dispersed in a medium consisting of a lowmolecular weight compound. The conductive elastomer composition had ahigh compression set. Thus the rubber roller composed of the conductiveelastomer composition was inappropriate. The rubber roller stained thephotosensitive member. Thus the conductive roller and the conductivebelt composed of the conductive elastomer composition were inappropriatefor practical use.

The conductive elastomer composition of the comparison example 6 isdifferent from that of the example 1 in that the copolymerization ratioamong the EP-EO-AGE terpolymer was EP:PO:AGE=90:4:6. The conductiveelastomer composition had a proper volume specific resistance value of10^(6.7) Ω·cm. But the conductive elastomer composition had a very highhardness and stained the photosensitive member. Thus the conductiveelastomer composition is inappropriate for practical use. The slab sheetcomposed of the conductive elastomer composition had a problem in itsresistance to water.

A foaming agent was added to the components of some of the examples toform the foams 1 through 6 composed of the conductive elastomercomposition shown in table 3.

To form the foams 1 through 6, the same EP-EO-AGE terpolymer as thatcontained in the conductive elastomer composition of the example 1 wasused as the base component. Two parts by weight of the anion-containingsalt having the fluoro group (F—) and the sulfonyl group (—SO₂—)(lithium-bis (trifluoromethanesulfonyl) imide), 7.5 parts by weight ofthe foaming agent, and additives shown in table 3 were added to theEP-EO-AGE terpolymer. The components were kneaded in a manner similar tothat of the example 1 to obtain the conductive elastomer composition ofeach of the foams 1 through 6. As the foaming agent, 4,4′-oxybis(benzene sulfonyl hydrazide) was used.

TABLE 3-1 Components Component (name (=trade name & maker)) Foam 1 Foam2 Foam 3 Epichlorohydrin rubber 1 (Trial product) 100 100 100 (EP:EO:AGE= 23:73:4, Mn = 130000, Mw = 580000) Inorganic filler 1 Calciumcarbonate light Maruo Calcium Kabushiki Kaisha 20 20 20Hydrotalcite-like compound DHT-4A-2 Kyowa Kagaku Kogyo Kabushiki Kaisha3 3 3 Magnesium oxide Magsarat 150ST Kyowa Kagaku Kogyo Kabushiki KaishaZinc oxide Two kinds of zinc oxide Mitsui Kinzoku Kabushiki Kaisha 5 5 5Stearic acid 4931 Unichema Australia 1 1 1 Lithium-bis 2 2 2(trifluoromethanesulfonyl) imide Foaming agent NeocelbonN#1000SW EiwaKagaku Kogyo Kabushiki Kaisha 7.5 7.5 7.5 Vulcanizing agent 1 Powderedsulfur Tsurumi Kagaku Kogyo Kabushiki Kaisha 1.5 1.00 0.50 Vulcanizingaccelerator 1 Nocceler DM Ouchi Shinko Kagaku Kogyo Kabushiki Kaisha 1.51.00 0.50 Vulcanizing accelerator 2 Nocceler TS Ouchi Shinko KagakuKogyo Kabushiki Kaisha 0.5 0.33 0.17 Vulcanizing agent 2 Accel 22-SKawaguchi Kagaku Kogyo Kabushiki Kaisha 0.67 1.33 Vulcanizingaccelerator 3 Nocceler DT Ouchi Shinko Kagaku Kogyo 0.57 1.13Vulcanizing agent 3 Actor BSH Kawaguchi Kagaku Kogyo Kabushiki Kaisha

TABLE 3-2 Components Component (name (=trade name & maker)) Foam 4 Foam5 Foam 6 Epichlorohydrin rubber 1 (Trial product) 100 100 100 (EP:EO:AGE= 23:73:4, Mn = 130000, Mw = 580000) Inorganic filler 1 Calciumcarbonate light Maruo Calcium Kabushiki Kaisha 20 20 20Hydrotalcite-like compound DHT-4A-2 Kyowa Kagaku Kogyo Kabushiki Kaisha3 Magnesium oxide Magsarat 150ST Kyowa Kagaku Kogyo Kabushiki Kaisha 3 3Zinc oxide Two kinds of zinc oxide Mitsui Kinzoku Kabushiki Kaisha 5 5 5Stearic acid 4931 Unichema Australia 1 1 1 Lithium-bis 2 2 2(trifluoromethanesulfonyl) imide Foaming agent NeocelbonN#1000SW EiwaKagaku Kogyo Kabushiki Kaisha 7.5 7.5 7.5 Vulcanizing agent 1 Powderedsulfur Tsurumi Kagaku Kogyo Kabushiki Kaisha 1.00 Vulcanizingaccelerator 1 Nocceler DM Ouchi Shinko Kagaku Kogyo Kabushiki 1.00Kaisha Vulcanizing accelerator 2 Nocceler TS Ouchi Shinko Kagaku KogyoKabushiki 1.65 0.8 Kaisha Vulcanizing agent 2 Accel 22-S KawaguchiKagaku Kogyo Kabushiki Kaisha 2.0 Vulcanizing accelerator 3 Nocceler DTOuchi Shinko Kagaku Kogyo 1.7 Vulcanizing agent 3 Actor BSH KawaguchiKagaku Kogyo Kabushiki Kaisha 3.18 1.06

The foam 1 contained the chemical foaming agent added to the componentsof the example 1. Sulfur (vulcanizing agent 1) was used as thevulcanizing agent.

The foam 2 contained the chemical foaming agent added to the componentsof the example 9. Sulfur (vulcanizing agent 1) and thiourea derivatives(vulcanizing agent 2) were used as the vulcanizing agent.

The foam 3 was similar to the foam 2, but had a smaller amount of thesulfur and the thiourea derivatives.

The foam 4 contained the chemical foaming agent added to the componentsof the example 3. Thiourea derivatives were used as the vulcanizingagent.

The foam 5 contained the chemical foaming agent added to the componentsof the example 10. Triazine derivatives was used as the vulcanizingagent.

The foam 6 contained the chemical foaming agent added to the componentsof the example 10. The sulfur and the triazine derivatives were used asthe vulcanizing agent.

An optimum amount of the foams 1 through 6 were sampled in anunvulcanized state to obtain a rubber specimen thereof. Thereafter inaccordance with “Die vulcanization test A-method” of “vulcanization testby using vibration type vulcanization testing machine” of JIS standard,a sine wave, not so destructive as to destroy the rubber specimen, whichhas a low amplitude (1° in the present invention) was applied to therubber specimen. A torque transmitted to an upper die from the rubberspecimen was measured. Vulcanization curves shown in FIG. 6 wereobtained. The temperature was set to 160° C.

As shown in table 6, it was confirmed that the foams 2 and 3 thatcontained the sulfur and the thiourea derivatives as the vulcanizingagent and the foam 6 which contained the sulfur and the triazinederivatives as the vulcanizing agent were much higher in thecrosslinking density and in the vulcanizing speed than the foam 1 whichcontained only the sulfur as the vulcanizing agent, the foam 4 whichcontained only the thiourea derivatives as the vulcanizing agent, andthe foam 5 which contained only the triazine derivatives as thevulcanizing agent.

As apparent from the foregoing description, according to the presentinvention, the anion-containing salt having the fluoro group (F—) andthe sulfonyl group (—SO₂—) is added to the ionic-conductive elastomercomponent providing uniform and stable electric resistance. Thereforethe conductive elastomer composition is capable of obtaining a very highconduction degree. Thus although the conductive elastomer composition isionic-conductive, it has a very low volume specific resistance value anda low compression set. Further the conductive elastomer composition hasa hardness suitable for composing the conductive roller and theconductive belt.

The epichlorohydrin, the ethylene oxide, the allyl glycidyl ether arecopolymerized at the predetermined ratio. The predetermined parts byweight of the anion-containing salt having the fluoro group (F—) and thesulfonyl group (—SO₂—) is added to the terpolymer of theepichlorohydrin-ethylene oxide-allyl glycidyl ether. Thus it is possibleto provide the conductive elastomer composition with a low volume changeand use the conductive elastomer composition suitably at a normaltemperature and humidity.

As apparent from the foregoing description, the conductive elastomercomposition of the present invention has a low electric resistance whichcannot be realized by the conventional one. Thus it can be used forvarious uses. More specifically, the charging roller, the developmentroller, the toner supply roller, the conductive belt, and the likecomposed of the conductive elastomer composition have small powerconsumption and contribute to formation of preferable images havinguniform density. The conductive elastomer composition can be usedsuitably for composing the conductive roller and the conductive beltsuch as the charging roller, the development roller, the toner supplyroller, the transfer belt, and the transfer roller for use in a colorcopying apparatus and a color printer. This is because the conductiveelastomer composition has a comparatively low electric resistance.Therefore the present invention provides image-forming apparatuses suchas the copying apparatus, the printer, the facsimile, and the like thathave small power consumption and provide preferable and high-qualityimages having uniform density reliably for a long time.

Examples 12 and 13 and comparison examples 7 and 8 will be described indetail below.

Components shown in table 4 were kneaded to prepare the solid conductiverubber roller composed of the conductive elastomer composition of eachof the examples 12 and 13 and comparison examples 7 and 8.

TABLE 4 Components Component (name (=trade name & maker) E12 E13 CE7 CE8Epichlorohydrin rubber 2 Epichlomer D Daiso Kabushiki Kaisha 40 50 40(EP:EO = 39:61) Epichlorohydrin rubber 3 Epichlomer CG104 DaisoKabushiki Kaisha 100 (EP:EO:AGE = 63:34.5:2.5) Acrylonitrile butadienerubber Nipol 401LL(NBR) Zeon 60 60 Chloroprene rubber Shoprene WRT(CR)Showa Denko 50 Inorganic filler 1 Calcium carbonate Maruo CalciumKabushiki Kaisha 20 20 20 20 light Hydrotalcite-like compound DHT-4A-2Kyowa Kagaku Kogyo Kabushiki Kaisha 3 3 3 3 Magnesium oxide Magsarat150ST Kyowa Kagaku Kogyo Kabushiki Kaisha Zinc oxide Two kinds of zincMitsui Kinzoku Kabushiki Kaisha 5 5 5 5 oxide Stearic acid 4931 UnichemaAustralia 1 1 1 Lithium-bis 1 1 (trifluoromethanesulfonyl) imide Lithiumtrifluoromethanesulfonate Lithium-tris (trifluoromethanesulfonyl)methane Ion-adsorbing agent Vulcanizing agent 1 Powdered sulfur TsurumiKagaku Kogyo Kabushiki Kaisha 1.5 0.5 1.5 1.5 Vulcanizing accelerator 1Nocceler DM Ouchi Shinko Kagaku Kogyo Kabushiki Kaisha 1.5 0.5 1.5 1.5Vulcanizing accelerator 2 Nocceler TS Ouchi Shinko Kagaku KogyoKabushiki Kaisha 0.5 0.17 0.5 0.5 Vulcanizing agent 2 Accel 22-SKawaguchi Kagaku Kogyo Kabushiki Kaisha 1.33 Vulcanizing accelerator 3Nocceler DT Ouchi Shinko Kagaku Kogyo Kabushiki Kaisha 1.13 Vulcanizingagent 3 Actor BSH Kawaguchi Kagaku Kogyo Kabushiki Kaisha Hardness 70 7271 73 Roller electric resistance 6.0 5.2 7.0 7.1 volume specificresistance 8.0 6.9 8.9 8.9 Compression set 27 5.3 27 28 Stain ofphotosensitive member ◯ ◯ ◯ ◯ Durability ◯ ◯ ◯ ◯ where E denotes exampleand where CE denotes comparison example.

The numerical values and abbreviations of table 4 are similar to thoseof tables 1 through 3. The conductive rubber roller, the propertyevaluation slab sheet, and the specimen of each of the examples 12 and13 and comparison examples 7 and 8 were prepared in methods similar tothose used in the examples 1 through 11 and the comparison examples 1through 6.

EXAMPLES 12 AND 13

The conductive elastomer composition of the example 12 contained onepart by weight of the anion-containing salt having the fluoro group (F—)and the sulfonyl group (—SO₂—) (lithium-bis (trifluoromethanesulfonyl)imide) added to 100 parts by weight of a mixture of the EP-EO bipolymerhaving the copolymerization ratio (EP:EO=39:61) falling in the rangespecified in the present invention and polar NBR, and the additivesshown in table 4 having the mixing ratio shown in table 4.

The conductive elastomer composition of the example 13 contained onepart by weight of the anion-containing salt having the fluoro group (F—)and the sulfonyl group (—SO₂—) (the lithium-bis(trifluoromethanesulfonyl) imide) added to 100 parts by weight of amixture of the EP-EO bipolymer having the copolymerization ratio(EP:EO=39:61) falling in the range specified in the present inventionand polar chloroprene rubber (CR), and the additives shown in table 4having the mixing ratio shown in table 4.

COMPARISON EXAMPLES 7 AND 8

The conductive elastomer composition of the comparison example 7contained 100 parts by weight of a mixture of the EP-EO bipolymer havingthe copolymerization ratio (EP:EO=39:61) falling in the range specifiedin the present invention and the polar NBR and the additives shown intable 4 having the mixing ratio shown in table 4. The conductiveelastomer composition did not contain the anion-containing salt havingthe fluoro group (F—) and the sulfonyl group (—SO₂—).

The conductive elastomer composition of the comparison example 8contained 100 parts by weight of the EP-EO-AGE terpolymer having thecopolymerization ratio (EP:EO:AGE=63:34.5:2.5) not falling in the rangespecified in the present invention and the additives shown in table 4having the mixing ratio shown in table 4. The conductive elastomercomposition did not contain the anion-containing salt having the fluorogroup (F—) and the sulfonyl group (—SO₂—).

The characteristics of the conductive elastomer composition of each ofthe examples 12 and 13 and comparison examples 7 and 8 were measured.Table 4 shows the results.

As indicated in table 4, the conductive elastomer composition of theexample 12 contained one part by weight of the anion-containing salthaving the fluoro group (F—) and the sulfonyl group (—SO₂—) (lithium-bis(trifluoromethanesulfonyl) imide) for 100 parts by weight of the mixturerubber containing 40 parts by weight of the EP-EO bipolymer having thecopolymerization ratio (EP:EO=39:61) falling in the range specified inthe present invention and 60 parts by weight of the polar NBR, thevulcanizing agent consisting of the sulfur, the accelerator consistingof the thiazole, and the vulcanizing accelerator consisting of thiuram.Therefore the conductive elastomer composition had a low volume specificresistance value, namely, 10^(8.0) (Ω·cm) and a proper compression setand hardness. The rubber roller did not stain the photosensitive member.Thus it was confirmed that the rubber roller was superior in itsproperties. Further the conductive elastomer composition was rated as ◯,namely, no problem in its resistance to water.

The conductive elastomer composition of the example 13 contained onepart by weight of the anion-containing salt having the fluoro group (F—)and the sulfonyl group (—SO₂—) (the lithium-bis(trifluoromethanesulfonyl) imide) for 100 parts by weight of the mixturerubber containing 50 parts by weight of the EP-EO bipolymer having thecopolymerization ratio (EP:EO=39:61) falling in the range specified inthe present invention and 50 parts by weight of the polar CR. Thereforethe conductive elastomer composition had a low volume specificresistance value, namely, 10^(6.9) (Ω·cm) and a proper compression setand hardness. The rubber roller did not stain the photosensitive member.Thus it was confirmed that the rubber roller was superior in itsproperties. Further the conductive elastomer composition was rated as ◯,namely, no problem in its resistance to water.

The conductive elastomer composition of each of the examples 12 and 13had a volume change not more than 10^(8.9) (Ω·cm) when the volume changewas measured at a voltage of 100V applied thereto in accordance with themethod specified in JIS K6911. The conductive elastomer composition hada compression set not more than 30% when the compression set wasmeasured at a temperature of 70° C. for 24 hours at a compressibilityratio of 25% in accordance with “the permanent set testing methods forrubber, vulcanized or thermoplastic” specified in JIS K6262. Theconductive elastomer composition had a hardness not more than 75 degreeswhen the hardness was measured by the durometer of type E. Further theconductive elastomer composition of each of the examples 12 and 13 didnot stain the photosensitive member and was thus excellent.

As indicated in table 4, the conductive elastomer composition of thecomparison example 7 is different from that of the example 12 in thatthe conductive elastomer composition of the comparison example 7 did notcontain the anion-containing salt having the fluoro group (F—) and thesulfonyl group (—SO₂—). The conductive elastomer composition had a largevolume specific resistance value, namely, more than 10^(8.5) Ω·cm. Thusthe conductive elastomer composition was inappropriate for practicaluse.

The conductive elastomer composition of the comparison example 8 isdifferent from that of the example 12 in that the conductive elastomercomposition of the comparison example 8 contained 100 parts by weight ofthe elastomer component, namely, the EP-EO-AGE terpolymer(EP:EO:AGE=63:34.5:25) and did not contain the anion-containing salthaving the fluoro group (F—) and the sulfonyl group (—SO₂—). Theconductive elastomer composition had a large volume specific resistancevalue, namely, more than 10^(8.5) Ω·cm. Thus the conductive elastomercomposition was inappropriate for practical use.

Examples 14 through 16 and comparison examples 9 through 11 will bedescribed in detail below.

Each of the roller of the examples 14 through 16 were formed by usingthe above-described method. The rollers of the examples 14 through 16contained the same components, shown in table 4, as those of theexamples 12 and 13. Each of the rollers of the comparison examples 9through 11 was also prepared by using the above-described method. Therollers of the comparison examples 9 through 11 contained the samecomponents, shown in tables 2 and 4, as those of the comparison examples3 and 4. The roller had an outer diameter of 16 mmφ and an innerdiameter (diameter of shaft) of 10 mmφ. The conductive elastomercomposition composing the roller of the examples 14 and 15 and thecomparison examples 9 and 10 contained 40 parts by weight of Hakuenka CC(produced by Shiraishi Calcium) for treatment of fatty acid. Theconductive elastomer composition composing the roller of the example 16and the comparison example 11 contained 50 parts by weight of weaklyconductive carbon black (#15 produced by Asahi Carbon Kabushiki Kaisha).

The roller of each of the examples 14 through 16 and the comparisonexamples 9 through 11 was mounted on a shaft having an inner diameter of10 mmφ and bonded to the shaft in an oven having a temperature of 160°C. Thereafter the end of the roller was shaped. Further the surfacethereof was polished to 20 mmφ and a predetermined surface roughness.The roller of the examples 14 and 15 and the comparison examples 9 and10 had a dielectric loss tangent of about 1.5. The roller of the example16 and the comparison example 11 had a dielectric loss tangent of about1.1. The dielectric loss tangent was measured at 100 Hz.

TABLE 5-1 E14 E15 CE9 CE10 Mixing E12 E12 CE7 CE3 UV irradiation 5minutes × 1/4 5 minutes × 1/4 Not irradiated 5 minutes × 1/4 of ofcircumferential of circumferential circumferential surface surfacesurface Finish polishing Polishing of Mirror-like Polishing of rollerPolishing of roller roller surface surface finish surface surfaceSurface roughness Rz 7.9 4.5 7.9 7.8 Friction coefficient μ 0.82 0.832.0 0.85 Roller electric resistance 6.2 6.2 7.2 6.0 With UV, With UV,With UV, Electric resistance ↑ Electric resistance ↑ Electric resistance↑ Evaluation by printing Appropriate Appropriate A little dark Smallcharged amount Epson LP2000C printed out 100 sheets of paper −16.5 −18.0−15.8 →Becomes dark Print density <25% halftone>   Dark Charged amount<printed by white solid> (μC/g)   −14.0 Evaluation of durability GoodGood Good wear a little Printed out 3000 sheets of paper Good ExcellentUneven (large Good Wear of sealing portion electric resistance,Stability of halftone poor toner-holding performance) Evaluation ◯ ⊚ ΔΔ~◯ where E denotes example and where CE denotes Comparison example.

TABLE 5-2 E16 CE11 Mixing E13 CE3 UV irradiation 5 minutes × 1/4 of 5minutes × 1/4 of circumferential circumferential surface surface Finishpolishing Mirror-like surface finish Polishing of roller surface Surfaceroughness Rz 4 4.5 Friction coefficient μ 0.80 0.82 Roller electricresistance 5.4 6.0 With UV, With UV, Electric resistance ↑ Electricresistance ↑ Evaluation by printing Appropriate Appropriate (BrotherHL1440) printed out 100 sheets of +39.5 +29.4 paper Print density <25%halftone> Charged amount <printed by white solid> (μC/g) Stability ofhalftone Excellent A little bad Evaluation ⊚ ◯~Δ where E denotes exampleand where CE denotes Comparison example.

After the surface of the roller of each of the examples 14 through 16and the comparison examples 9 through 11 was washed with water, thesurface of each roller was irradiated with ultraviolet rays to form anoxide layer thereon. An ultraviolet ray irradiator (produced by SenTokushu Kogen Kabushiki Kaisha, PL21-200) irradiated the surface of eachroller with ultraviolet rays (184.9 nm and 253.7 nm) at an angle of 90degrees in the circumferential direction thereof for a predeterminedperiod of time, with the roller and an ultraviolet ray lamp spaced fromeach other at 10 cm. The roller was rotated at 90 degrees four times toform the oxide film on the entire peripheral surface (360 degrees)thereof. The roller of the examples 14 and 15 and the comparisonexamples 9 and 10 had a dielectric loss tangent of about 1.1. The rollerof each of the example 16 and the comparison example 11 had a dielectricloss tangent of about 0.5. The dielectric loss tangent was measured at100 Hz.

The following properties were measured on the conductive elastomercomposition of each of the examples 14 through 16 and the comparisonexamples 9 through 11. Table 5 shows the results in the lower portionthereof. The electric resistance value of each roller was measured byusing the above-described method.

Measurement of Dielectric Loss Tangent

As shown in FIG. 7, an alternating voltage of 100 Hz to 100 kHz wasapplied to electrodes, namely, a shaft 22 and a metal plate 23 on whicha rubber roller 21 was placed. An R (electric resistance) component anda C (capacitor) component were measured separately by an LCR meter(AG-4311B, manufactured by Ando Denki) at a temperature of 23° C. to 24°C. (room temperature). The dielectric loss tangent, the impedance, andthe phase angle were found by using the following equation.Dielectric loss tangent (tan δ)=G/ωCG=1/R

The dielectric loss tangent was found as G/ωC by modeling the electricalcharacteristic of one roller as a parallel equivalent circuit of theelectric resistance component thereof and that of the capacitorcomponent.

Measurement of Surface Roughness

The surface roughness Rz was measured in accordance with JIS B 0601(1994).

Measurement of Friction Coefficient

As shown in FIG. 8, numerical values obtained by a measuring apparatushaving a digital force gauge “Model PPX-2T” 31, a friction piece (OHPfilm commercially available) 32, a 20 g-weight 34, and a conductiverubber roller 33 was substituted into Euler's equations to compute thefriction coefficient.

Printing Test

To examine adhesiveness of charged toner, electric uniformity of thecharged toner, time stability (durability), i.e., to evaluate theperformance of the rubber roller of each of the examples and thecomparison examples, the rubber roller of the examples 14, 15 and thatof each of the comparison examples 9, 10 were mounted on a printerLP2000C of non-contact type manufactured by Epson Inc., whereas therubber roller of the example 16 and that of the comparison example 11were mounted on a printer (HL1440 manufactured by Brother Industries,Inc.) of contact type to check formed images.

The quality of each image (initial image) was evaluated by the degree ofunevenness of density thereof, when a 25% halftone image was formed on100 sheets of paper. After printing was performed, toner disposedproximate to the photosensitive member was sucked by a charged quantitymeasuring apparatus to measure the charged quantity thereof and theweight of the sucked toner by a weight meter. The quantity of staticelectricity per weight was computed as the charged quantity (μC/g).

The durability of each rubber roller was evaluated as the stabilitydegree of halftone by printing out 3000 (half of indicated number)sheets of paper before a toner box was empty. That is, the degree ofwear of a sealing portion was checked, and the difference between thequality of an initial image and that of an image formed on 3000th paperwas compared with each other.

The oxide layer was formed on the surface of the roller of each of theexamples 14 through 16 by irradiating the surface thereof withultraviolet rays to set the surface roughness Rz and the frictioncoefficient to the range specified in the present invention. Thereforeeach roller had a preferable electric resistance value and preferableperformance in the printing test. There is a possibility of discharge inthe printer of non-contact type when the electric resistance value ofthe roller is smaller than 10⁵. But each roller had a preferableelectric resistance value. Thus no discharge occurred.

It has been found that the conductive roller of the present invention isapplicable to printers of non-contact type and contact type.

On the other hand, the oxide layer was not formed on the surface of theroller of the comparison example 9. And the roller had a higher electricresistance value, because of the salt. So the roller did not havepreferable performance in the printing test. Thus the evaluation wasgenerally unfavorable.

The oxide layer was formed on the surface of the roller of each of thecomparison examples 10 and 11. However, the components of the conductiveelastomer composition of the comparison examples 10 and 11 were notincluded in the scope of the present invention. Thus the rollers did notpreferable performance in the printing test. Thus the evaluation wasgenerally unfavorable.

The results indicate that the conductive elastomer composition composedof the conductive elastomer composition containing the mixture rubber ofthe EP-EO bipolymer having the copolymerization ratio (EP:EO=39:61) andthe polar CR and the anion-containing salt having the fluoro group (F—)and the sulfonyl group (—SO₂—) (the lithium-bis(trifluoromethanesulfonyl) imide) has a low volume specific resistancevalue. Thus the conductive roller can be suitably used as thedevelopment roller. Further the conductive rubber roller has a propercompression set and hardness. Furthermore the conductive rubber rollerdoes not stain the photosensitive member and displays preferablecharacteristics in the printing test.

1. A conductive elastomer composition comprising an ionic-conductiveelastomer component, and an anion-containing salt having a fluoro group(F—) and a sulfonyl group (—SO₂—), said conductive elastomer compositionhaving: a volume charge not more than 10^(6.9) (Ω·cm) when said volumecharge is measured at a voltage of 100V applied thereto in accordancewith the method specified in JIS K6911; a compression set not more than30% when said compression set is measured at a temperature of 70° C. for24 hours at a compressibility ratio of 25% in accordance with “thepermanent set testing methods for rubber, vulcanized or thermoplastic”specified in JIS K6262, and a hardness not more than 75 degrees whensaid hardness is measured by a durometer of type E specified in JISK6253, and wherein said conductive elastomer composition is a vulcanizedrubber composition comprising: epihalohydrin rubber, as saidionic-conductive elastomer component, which comprises epihalohydrin,ethylene oxide, and allyl glycidyl ether copolymerized at a ratio of 10to 45 mol %, 55 to 80 mol %, and 0 to 10 mol % respectively; and notless than 0.01 nor more than 20 parts by weight of said anion-containingsalt having said fluoro group (F—) and said sulfonyl group (—SO₂—) for100 parts by weight of an entire polymer component containing saidionic-conductive elastomer component.
 2. The conductive elastomercomposition according to claim 1, having a volume change less than 50%when said conductive elastomer composition is immersed in distilledwater at 40±1° C. for 22±0.25 hours.
 3. The conductive elastomercomposition according to claim 1, wherein as said epihalohydrin rubber,epichlorohydrin rubber is used.
 4. The conductive elastomer compositionaccording to claim 1, wherein said anion-containing salt having saidfluoro group (F—) and said sulfonyl group (—SO₂—) includes at least onesalt selected from among a salt of bisfluoroalkylsulfonylimide, a saltof tris (fluoroalkylsulfonyl) methane, and a salt of fluoroalkylsulfonicacid.
 5. The conductive elastomer composition according to claim 1,wherein a terpolymer of epichlorohydrin-ethylene oxide-allyl glycidylether is used singly or a mixture of chloroprene rubber and saidterpolymer of said epichlorohydrin-ethylene oxide-allyl glycidyl etheris used, and said terpolymer of said epichlorohydrin-ethyleneoxide-allyl glycidyl ether or said mixture is crosslinked with sulfurand thiourea derivatives in combination or with said sulfur and triazinederivatives in combination.
 6. A conductive elastomer compositionaccording to claim 1, having a dielectric loss tangent in a range from0.1 to 1.5.
 7. A conductive member composed of a conductive elastomercomposition according to claim
 1. 8. The conductive member according toclaim 7, which is a conductive roller or a conductive belt.
 9. Theconductive member according to claim 8, wherein the conductive roller isa development roller.
 10. A conductive member composed of a conductiveelastomer composition according to claim 1, having a surface roughnessRz not less than 1 μm nor more than 8 μm; and a surface frictioncoefficient in a range from 0.1 to 1.5.
 11. A conductive member composedof a conductive elastomer according to claim 1, having a surface made ofan oxide film.
 12. The conductive member according to claim 11, whereinsaid oxide film formed on said surface is formed by irradiating saidsurface with ultraviolet rays and/or ozone.